CHAPTER V.

ON SEASONING TIMBER BY PATENT PROCESSES, ETC.

Long years of practical experience has shown that timber, however prone to dry or wet rot, may be preserved from both by the use of certain metallic solutions, or other suitable protective matters.

All the various processes may be said somewhat to reduce the transverse strength of the timber when dry, and the metallic salts are affected at the iron bolts or fastenings. The natural juices of some woods do this; and bolts which have united beams of elm and pitch pine will often corrode entirely away at the junction.

The processes adopted for resisting the chemical changes in the tissues of the wood are all founded on the principle that it is essential to inject some material which shall at once precipitate the coaguable portion of the albumen retained in the tissues of the wood in a permanent insoluble form, so that it will not hereafter be susceptible of putrefactive decomposition. For this purpose, many substances, many solutions, have been employed with variable success, but materials have been sometimes introduced for this purpose which produced an effect just the opposite to what was anticipated.

Experience has shown that timber is permeable, at least by aqueous solutions, only so long as the sap channels are free from incrustation.

Such in general is the case with beech, elm, poplar, and hornbeam, the capillary tubes of which are always open, or, at least, close very slowly. At the same time it may be said that there must remain ever in these species some parts impervious to injection, whilst it is almost impossible but that a certain portion of the fibres will be more or less incrusted. The sap woods, on the other hand, of every species appear quite pervious.

Very little is known of any preservative process adopted in ancient times. Pliny observes that the ancients used garlic boiled in vinegar with considerable success, especially with reference to preserving timber from worms: he also states that the oil of cedar will protect any timber anointed with it from worm and rottenness. Oil of cedar was used by the ancient Egyptians for preserving their mummies. Tar and linseed oil were also recommended by him. The image of the goddess Diana, at Ephesus, was saturated with olive and cedar oils; also the image of Jupiter, at Rome; and the statues of Minerva and Bacchus were impregnated with oil of spikenard.

The idea of preserving wood by the action of oil is therefore by no means new; but it is somewhat curious that the earliest modern processes should also be by means of oil. The _oils most proper_ to be used are _linseed_, _rapeseed_, or almost any of the vegetable fixed oils. Oak wood, rendered entirely free from moisture, and then immersed in linseed oil, is said to be thus prevented from splitting: the time of immersion depending on the size, &c. Palm oil is preferable to whale oil, because impregnation with the latter, although in many instances eligible, causes wood to become brittle. It is, however, probable that whale oil, when combined with other substances, such as litharge, coal pitch, or charcoal, may lose much of that effect. As cocoa-nut oil, which is, under low temperature, like the oil expressed from the nuts of the palm tree, is known to be highly preservative of timber and metallic fastenings, we may expect the same result from the latter, and thereby avoid that extreme dryness and brittleness of the timber which Mr. Strange complained of in the Venetian ships that had been seasoned for many years in frame under cover. Cocoa-nut oil beat up with shell lime or _chunam_, so as to become putty, and afterwards diluted with more oil, is used at Bombay and elsewhere as a preservative coat or varnish to plank. It cannot become a varnish without the addition of some essential oil; and the oil of mustard is used; which, of course, will produce the desired effect. In the first volume of the Abbé Raynal, on the European settlements in the East and West Indies, he mentions that an oil was exported from Pegu for the preservation of ships; but as he does not say what oil, no conclusion can be drawn further than as to the probability of its being one of those already noticed.

Experience has proved that even _animal oils_ are so far injurious to timber as to _render it brittle_, whilst they preserve it from rottenness; and that, on the other hand, a mineral salt more or less combined with fatty substances does not produce that effect. The staves of whale-oil casks become quite brittle, whilst those of beef, pork, and tallow barrels remain tough and sound. Ships _constantly_ in the Greenland trade have their timbers and planks preserved so far as they have become impregnated with whale oil.

Experiments with fish oil prove that of itself, unless exposed to sun and air, it may be injurious; that it loosens the cohesion of timber; but that _animal fat_, combined _with saline matter_, _is preservative_.

Fish oil used alone is ineligible, because capable of running into the putrefactive process, unless as a thin outside varnish. In hard, sound timber, it will hardly enter at all; and if poured into bore-holes in the heads of timbers, it will insinuate itself into the smallest rents or cracks, and waste through them. Used alone, or with any admixture, it is absorbed and dried quickly on wood in a decomposing state or commencing to be dry rotten. Used with litharge, it dries after some days; but with lamp-black it has scarcely so much tendency to dry as when used alone. Paint of fish oil and charcoal dries very quickly where there is absorption, and the charcoal extends its oxidating or drying effect to the fish oil in its vicinity.

We give the following to prove what we have written, and also to serve as an example for those who wish to try experiments:--

EXPERIMENTS ON FISH OIL.

June 9.--Upon a piece of old oak scantling, with its alburnam on one side in a state of decay, fish oil was poured several times, viz. on this day, on June 25, and July 3, which it rapidly absorbed in the decayed part.

July 26.--It was payed (or mopped) with fish oil and charcoal powder, and the following day it was put under an inverted cask.

October 1.--The end of this piece was covered with a greenish mould. _This proves that fish oil must be injurious, except where exposed to sun and air to dry it._

A compound of fixed oils and charcoal is liable to inflame, but as a thin covering or pigment it may not be so.

The _petroleum_ oil-wells, near Prome, in Burmah, have been in use from time immemorial. Wood, both for ship-building and house-building, is invariably saturated or coated with the product of those wells; and it is stated that the result is _entire immunity from decay_ and the ravages of the white ant. At Marseilles, and some other ports in the Mediterranean, it used to be the practice to run the petroleum, which is obtained near the banks of the Rhone, into the vacancies between the timbers of the vessels, to give them durability. It was sometimes, for the conjoint purpose of giving stability and duration to vessels, mixed with coarse sand or other extraneous matters, and run in whilst hot between the ceiling and bottom plank, where it filled up the vacancies between the timbers in the round of their bottoms, excepting where necessary to be prevented. The great objection to the use of petroleum is its inflammability. _Creosote_, its great rival for wood preserving, is also inflammable, and not so agreeable in colour; but it is _considerably cheaper_, which is an important matter.

As we are now about to enter upon the subject of patent processes, &c., it appears desirable to lay down certain principles at the commencement, in order to assist the reader as much as possible.

Almost every chemical principle or compound of any plausibility has been suggested in the course of the last hundred and fifty years; but the multiplicity and contradiction of opinions form nearly an inextricable labyrinth. To commence.

1st. It seems obvious that _the sooner the sap is wholly removed from the wood the better_, _provided the woody fibre solidifies without injury_.

2nd. That _the wood should be impregnated with any strongly antiseptic and non-deliquescent matter_, _which must necessarily be in solution when it enters the wood_. No deliquescent remedy is eligible, because moisture is injurious to metallic fastenings.

3rd. _The wood should be first dried, and its pores then closed with any substance impervious to air and moisture, and at the same time highly repellant to putrescency._ The most essential requisites in a preservative of timber being a disposition to _dryness_, and a tendency to resist _combustion_ as far as consistently obtainable.

4th. _Any process to be successful ought not to be tedious, very difficult, or too expensive._ These are important elements in the success of any patent.

Very little is known of any preservative process previous to the year 1717, when directions were given by the Navy authorities to _boil_ treenails, and dry them before they were used. But whether the custom had prevailed before this time, or whether their strength and durability were increased by it, there are no means of ascertaining. It does not appear that any substance was put into the water to decompose the juices; but as they are soluble in warm water, perhaps the power of vegetation might have been destroyed without it.

In 1737 Mr. Emerson patented a process of saturating timber with _boiled oil_, mixed with poisonous substances; but his process was very little used. This, we believe, was the _first_ patent on wood preserving.

About 1740, Mr. Reid proposed to arrest decay by means of a certain _vegetable acid_ (probably pyroligneous acid). The method of using it was by simple immersion.

In 1756, Dr. Hales recommended that the planks at the water-line of ships should be soaked in _linseed oil_, to prevent the injury to which wood is subject when alternately exposed to wet and dry; and indeed, many ships were built in which a hollow place was cut in one end of each beam or sternpost, which might constantly be kept filled with _train oil_. Amongst other ships so constructed, the ‘Fame,’ 74, may be mentioned. When, after some years, this ship was repaired, it was found that as far as the oil had penetrated, namely, from 12 to 18 inches from the end, the wood was quite sound, whilst the other parts were more or less decayed. The Americans used to hollow out the tops of their masts in the form of cups or basins; bore holes from the end a considerable way down the masts; pour oil into these; cover them over with lead; and leave the oil to find its way down the capillary vessels to the interior of the timber.[7]

In 1769, Mr. Jackson, a London chemist, with a view to the prevention of decay, obtained permission to prepare some timber to be used in the national yards, by immersing it in a solution of _salt water_, _lime_, _muriate of soda_, _potash_, _salts_, &c., the result of which dose was, that several frigates in the Navy subjected to the process were rendered more perishable than if they had been constructed of unprepared timber. The solution was filtered into the wood partly by means of holes made in it. Chapman proposed a similar method of preserving the frames of ships, viz. by boring holes in the timbers, and pumping a _solution of copperas_ in water into them. He believed every part of the vessel would thus be impregnated.

Mr. Jackson also prepared the frame of the ship ‘Intrepid’ with another solution. The ship lasted many years. Bowden thought it was a _solution of glue_. Chapman suggested _slaked lime_, thinned with a weak _solution of glue_ for mopping the timbers of a ship.

Shortly after Mr. Jackson’s process was started, Mr. Lewis attempted to accomplish the preservation of timber by placing it surrounded by pounded lime, in spaces below the “surface of the earth.” The use of lime has also been advocated by Mr. Knowles, Secretary of the Committee of Surveyors of the Navy, who has written an able work on the ‘Means to be taken to Preserve the British Navy from Dry Rot’ (1821).

Between 1768 and 1773 a practice prevailed of saturating ships with common salt; but this was found to cause a rapid corrosion of the iron fastenings, and to fill the vessels between decks with a constant damp vapour. In ‘Nicholson’s Journal,’ No. 30, there is an article signed _Nauticus_ on this subject. Vessel owners had long ago observed that those ships which have early sailed with cargoes of salt are not attacked by dry rot. Indeed, several instances are attested of vessels whose interiors were lined with fungi having all traces of the plant destroyed by accidental or intentional sinking in the sea. Acting on such hints, a trader of Boston, U. S., salted his ships with 500 bushels of the chloride, disposed as an interior lining, adding 100 bushels at the end of two years. Such an addition of dead weight is sufficient objection to a procedure which has other great disadvantages. Salt should never be applied as an antidote against the dry rot, on account of its natural powers of attracting moisture from the atmosphere, which would render apartments almost uninhabitable, from their continual dampness. Those who have lived for any length of time in a house at the sea-side, the mortar of which has been partly composed of sea sand, will have observed the moist state of the paper, plastering, &c., in wet weather. Bricks made with sea sand are objectionable.

_Salt water_ seasoning has already been referred to in the last chapter, but as it is so closely connected with salt seasoning, the further and final consideration of salt water seasoning may be fitly dealt with here. Salt water will not extract the juices from the timber like fresh water. It is only by destroying the vegetation that salt water can be advantageous, but it would require a very long time to impregnate large timber to the heart so as to destroy vegetation. It is well known that wood is softened, and in time decomposed, by extreme moisture. Fifty years since, the master builder at Cronstadt complained that the oak from Casan, which was frequently wet from different causes in its passage of three years to Cronstadt, was so water-soaked as never to dry; and also from the information of Mr. Strange, it appears “that the practice at Venice of the fresh-cut timber being thrown into salt water, prevents its ever becoming dry in the ships, and that the salt water rusted and corroded the iron bolts.” In fine, vessels built with salt water seasoned wood are perfect hygrometers, being as sensible to the changes of the moisture of the atmosphere as lumps of rock salt, or the plaster of inside walls where sea sand has been used.

In Ceylon, the timber of the female palm tree is much harder and blacker than that of the male, inasmuch as it brings nearly triple its price. The natives are so well aware of the difference that they resort to the devise of immersing the male tree in _salt water_ to deepen its colour, as well as add to its weight.

Vessels impregnated with _bay salt_, or the large grained salt of Leamington or of Liverpool (pure muriate of soda), will possess decided advantages; as also will vessels that have been laden with _saltpetre_, if it has been dispersed amongst their timbers.

Ships (the timbers of which had been previously immersed in salt water) have been broken up after a few years’ service, and the floor timbers taken out quite sound: but when exposed to the sun and rain in the summer months, their albumen has been in a decomposed or friable state.

By the answers to queries given to Mr. Strange, the British Minister at Venice, in or about 1792, it appears that several of the Venetian ships of war had then lain under sheds for fifty-nine years; some in bare frames, and others planked and caulked: that these ships show no outward marks of decay; but their timbers have shrunk much, and _become brittle_; that some of the most intelligent ship builders were of opinion that great prejudice had arisen from the prevalent custom of throwing the timber fresh cut into salt water, and letting it lie there until wanted; that afterwards it dried, and withered on the outside, under the sheds, while the inside, being soaked with salt water, rotted before it became dry; and this was one reason, amongst others, why Venetian ships, though built of good timber, lasted so short a time; for the salt moisture not only rots the inside of the beams and timbers, but of course rusts and corrodes the iron bolts.

_Salt water_, _sea-sand_, and _sea-weed_ are now used for seasoning “jarrah” wood in Western Australia. This wood is considered a first-class wood for ship-building, but it is somewhat slow to season, and if exposed before being seasoned it is apt to “fly” and cast. The method adopted is as follows: The logs are thrown into the sea, and left there for a few weeks; they are then drawn up through the sand, and after being covered with sea-weed a few inches deep, are left to lie on the beach, care being taken to prevent the sun getting at their ends. The logs are then left for many months to season. When taken up they are cut into boards 7 inches wide, and stacked, so as to admit of a free circulation of air round them, for five or six months before using them. Sea-weed or sea-ware, cast upon the shores, contains a small quantity of carbonate of soda, and a large proportion of nitrogenous and saline matters, with earthy salts, in a readily decomposable state. They also contain much soluble mucilage. The practice of seasoning timber by heating it in a _sand bath_ was formerly adopted by the Dutch, and by the Russians in building boats. Mr. Thomas Nichols (in a letter to Lord Chatham, when First Lord of the Admiralty) states “that the same end, viz. preservation of timber from decay, might probably be acquired by burying the timber in sand, which acts as an artificial sap,” in the same manner as mentioned in Townsend’s ‘Travels through Spain,’ to be used with the masts of ships of war at Cadiz.

_Peat moss_ has been recommended (because the sulphates of iron, soda, and magnesia are found in it), but it failed when tried.

With reference to Mr. Lewis’s proposal to preserve wood by means of lime, it must be remembered that _quicklime_, with damp, has been found to accelerate putrefaction, in consequence of its extracting carbon; but when dry, and in such large quantities as to absorb all moisture from the wood, _the wood is preserved_, _and the sap hardened_. Vessels _long_ in the lime trade have afforded proof of this fact; and we have also examples in plastering-laths, which are generally found sound and good in places where they have been dry. Whitewash or _limewater_ has been strongly recommended for use between the decks of ships, as being unfavourable to vegetation: it should be renewed at intervals of time, according to circumstances. It has been applied with good effect to the joists and sleepers of kitchen floors; but to be effectual it should be occasionally renewed. Effete, or re-carbonated lime, is injurious to timber, like other absorbent earths; so also are calcareous incrustations formed by the solution of lime in water, as appears from Von Buch’s ‘Travels in Norway,’ in which he says, “that in the fishing country (near Lofodden, beyond the Arctic circle) the calcareous incrustations brought by water, filtering through a bed of shells, soon cause the vessels and wood to be covered with and destroyed by green fungi.” The ends of joists of timber inserted in walls are frequently found rotten; and where not so, it may probably be owing to the mortar having been made with hot lime, and used immediately, or to the absence of moisture. It does not appear practicable to use limewater to any extent for preserving timber, because water holds in solution only about ⅟500th part of lime, which quantity would be too inconsiderable; it, however, renders timber more durable, but at the same time very hard and difficult to be worked (p. 73).

Vessels constantly in the _coal_ trade have generally required little repair, and have lasted until in the common course of things they were lost by shipwreck. This must be owing to the martial pyrites which abound in all coals; and also from the sulphuric acid arising from the quantity of coal dust which finds its way through the seams of the ceiling, and adheres to the timber and planks.

In 1779, M. Pallas, in Russia, proposed to steep wood in _sulphate of iron_ (green vitriol) until it had penetrated deeply, _and_ then in _lime_ to precipitate the vitriol. Neumann, in his first volume of ‘Chemistry,’ on the article green vitriol, says, “That in the Swedish transactions this salt is recommended for preserving wood, particularly the wheels of carriages, from decay.

“When all the pieces are fit for being joined together, they are directed to be boiled in a solution of vitriol for three or four hours, and then kept for some days in a warm place to dry. It is said that the wood by this preparation becomes so hard and compact that moisture cannot penetrate it, and that iron nails are not so apt to be destroyed in this vitriolated wood as might be expected, _but last as long as the wood itself_.”

In 1780 the marcasite termed by the miners _mundic_, found in great abundance in the tin mines in Devonshire and Cornwall, was employed, in a state of fusion, to eradicate present and to prevent the future growth of dry rot; but whether its efficacy was proved by time is not known. A garden walk where there are some pieces of mundic never has any weeds growing; the rain that falls becomes impregnated with its qualities, and in flowing through the walk prevents vegetation.

In 1796 Hales proposed to _creosote_ the treenails of ships: this was forty-two years previous to Bethell’s patent for creosoting wood.

About the year 1800, the Society of Arts’ building in the Adelphi, London, being attacked by dry rot, Dr. Higgins examined the timbers, caused some to be removed and replaced by new, and the remainder to be scraped and washed with a solution of _caustic ammonia_, so as by burning the surface of the wood to prevent the growth of fungi.

At the commencement of the present century, a member of the Royal Academy of Stockholm called attention to the use of _alum_ for preserving wood from fire. He says, in the Memoirs of that Academy, “Having been within these few years to visit the alum mines of Loswers, in the province of Calmar, I took notice of some attempts made to burn the old staves of tubs and pails that had been used for the alum works. For this purpose they were thrown into the furnace, but those pieces of wood which had been _penetrated_ by the alum did not burn, though they remained for a long time in the fire, where they only became red; however, at last they were consumed by the intenseness of the heat, but they yielded no flame.” He concludes, from this experiment, that wood or timber for the purpose of building may be secured against the action of fire by letting it remain for some time in water wherein vitriol, alum, or any other salt has been dissolved which contains no inflammable parts.

In Sir John Pringle’s Tables of the antiseptic powers of different substances, he states _alum_ to be thirty times stronger than sea-salt; and by the experiments of the author of the ‘Essai pour servir à l’Histoire de la Putréfaction,’ metallic salts are much more antiseptic than those with earthy bases.

In 1815 it occurred to Mr. Wade that it would be a good practice to fill the pores of timber with _alumine_, or selenite; but two years after, Chapman observed, “Impregnation of ships’ timbers with a _solution of alum_ occurred to me about twenty years since, because on immersion in sea-water the alumine would be deposited in the pores of the timber; but I was soon informed of its worse than inutility, by learning that the _experiment had been tried_, and, in place of preserving, had _caused the wood to rot speedily_. Impregnation with _selenite_ has been tried in elm water-pipes. On precipitation from its solvent it partially filled the pores, and hardened the wood, but _occasioned speedy rottenness_.” If, by using a _solution of alum_ to render wood uninflammable, we at the same time cause it to _rot speedily_, it becomes a question _whether the remedy is not worse than the disease_. Captain E. M. Shaw, of the London Fire Brigade, in his work, ‘Fire Surveys’ (1872), recommends _alum and water_. Probably he only thought of fire, and not of rotting the wood. The alum question does not appear to be yet satisfactorily settled.

While upon the subject of uninflammable wood, we may state that in 1848, upon Putney Heath (near London), by the roadside, stood an obelisk, to record the success of a discovery made in the last century of the means of building a house which no ordinary application of ignited combustibles could be made to consume: the obelisk was erected in 1786. The inventor was Mr. David Hartley, to whom the House of Commons voted 2500_l._, to defray the expenses of the experimental building, which stood about one hundred yards from the obelisk. The building was three stories high, and two rooms on a floor. In 1774, King George the Third and Queen Charlotte took their breakfast in one of the rooms, while in the apartment beneath fires were lighted on the floor, and various inflammable materials were ignited to attest that the rooms above were fire-proof. Hartley’s secret lay in the floors being double, and there being interposed between the two boards sheets of laminated iron and copper, not thicker than stout paper, which rendered the floor air-tight and thereby intercepted the ascent of the heated air; so that, although the inferior boards were actually charred, the metal prevented the combustion taking place in the upper flooring. Six experiments were made by Mr. Hartley in this house in 1776, but we cannot ascertain any particulars about them, or any advantages which accrued to the public from the invention, although the Court of Common Council awarded him the freedom of the City of London for his successful experiments.

In 1805 Mr. Maconochie proposed to saturate with resinous and oily matters inferior woods, and thus render them more lasting. This proposal was practically carried out in 1811 by Mr. Lukin, who constructed a peculiar stove for the purpose of thus impregnating wood under the influence of an increased temperature. The scheme, however, had but very partial success, for either the heat was too low and the wood was not thoroughly aired and seasoned, or it was too high and the wood was more or less scorched and burnt. Mr. Lukin buried wood in _pulverized charcoal_ in a heated oven, but the fibres were afterwards discovered to have started from each other. He next erected a large kiln in Woolwich dockyard, capable of containing 250 loads of timber, but an explosion took place on the first trial, before the process was complete, which proved fatal to six of the workmen, and wounded fourteen, two of whom shortly afterwards died. The explosion was like the shock of an earthquake. It demolished the wall of the dockyard, part of which was thrown to the distance of 250 feet; an iron door weighing 280 lb. was driven to the distance of 230 feet; and other parts of the building were borne in the air upwards of 300 feet. The experiment was not repeated.

Mr. Lukin was not so fortunate in 1811 as in 1808, for in the latter year he received a considerable reward from the Government for what was considered a successful principle of ventilating hospital ships.

In 1815 Mr. Wade recommended the impregnation of timber with resinous or oleaginous matter (preferring linseed oil to whale oil) or with _common resin_ dissolved in a lixivium of _caustic alkali_, and that the timber should afterwards be plunged into water acidulated with any cheap acid, or with alum in solution. He considered that timber impregnated with oil would not be disagreeable to rats, worms, cockroaches, &c., and that the contrary was the case with resin. He also recommended the impregnation of timber with sulphate of _copper, zinc, or iron_, rejecting deliquescent salts, as they corrode metals.

In 1815 Mr. Ambrose Boydon, of the Navy Office, strongly recommended that the timber, planks, and treenails of ships should be first boiled in _limewater_ to correct the acid, and that they afterwards should be boiled in a _thin solution of glue_, by which means the pores of the wood would be filled with a hard substance insoluble by water, which would not only give the timbers durability, by preventing vegetation, but increase their strength. Glue, he thought, might be used without limewater, or glue and limewater mixed together.

In 1817 Mr. William Chapman published the result of various experiments he had made on wood with _lime_, _soap_, and _alkaline_ and _mineral salts_. He recommended a solution of a pound of _sulphate of copper_ or blue vitriol (at that time 7_d._ per pound) dissolved in four ale gallons of rain water, and mopped on hot over all the infected parts, or thrown over them in a plentiful libation. He also recommended one ounce of _corrosive sublimate_ (then 6_s._ per pound) to a gallon of rainwater applied in the same manner to the infected parts. For weather-boarded buildings he considered one or more coats of thin _coal tar_, combined with a small portion of _palm oil_, for the purpose of preventing their tendency to rend, to be a good preservative.

Messrs. Wade, Boydon, and Chapman published works on dry rot about this time.

In 1822 Mr. Oxford took out a patent for an improved method of preventing “decay of timber,” &c. The process proposed was as follows: “The essential _oil of tar_ was first extracted by distillation, and at the same time saturated with _chlorine gas_. Proportions of _oxide of lead_, _carbonate of lime_, and _carbon of purified coal tar_ well ground, were mixed with the oil, and the composition was then applied in thick coatings to the substances intended to be preserved.”

On 31st March, 1832, Mr. Kyan patented his process of _corrosive sublimate_ (solution of the _bi-chloride of mercury_) for preventing dry rot; which process consisted as follows: A solution of the corrosive sublimate is first made, and the timber is placed in the tank. The wood is held down in such a way, that when immersed on the fluid being pumped in, it cannot rise, but is kept under the surface, there being beams to retain it in its place. There it is left for a week, after which the liquor is pumped off, and the wood is removed. This being done, the timber is dried, and said to be prepared. Sir Robert Smirke was one of the first to use timber prepared by Kyan, in some buildings in the Temple, London; and he made some experiments on timber which had undergone Kyan’s process. He says, “I took a certain number of pieces of wood cut from the same log of yellow pine, from poplar, and from the common Scotch fir; these pieces I placed first in a cesspool, into which the waters of the common sewers discharged themselves; they remained there six months; they were then removed from thence, and placed in a hotbed of compost under a garden-frame; they remained there a second six months; they were afterwards put into a flower border, placed half out of the ground, and I gave my gardener directions to water them whenever he watered the flowers; they remained there a similar period of six months. I put them afterwards into a cellar where there was some dampness, and the air completely excluded; they remained there a fourth period of six months, and were afterwards put into a very wet cellar. Those pieces of wood which underwent Kyan’s process are in the same state as when I first had them, and all the others to which the process had not been applied are more or less rotten, and the poplar is wholly destroyed.

“I applied Kyan’s process to yellow Canadian pine about three years ago, and exposed that wood to the severest tests I could apply, and it remains uninjured, when any other timber (oak or Baltic wood) would certainly have decayed if exposed to the same trial, and not prepared in that manner.

“As another example of the effect of the process, I may mention that about two years ago, in a basement story of some chambers in the Temple, London, the wood flooring and the wood lining of the walls were entirely decayed from the dampness of the ground and walls, and to repair it under such circumstances was useless. As I found it extremely difficult to prevent the dampness, I recommended lining the walls and the floor with this prepared wood, which was done; and about six weeks ago I took down part of it to examine whether any of the wood was injured, but it was found in as good a state as when first put up. I did not find the nails more liable to rust.’

“I have used Kyan’s process in a very considerable quantity of paling nearly three years ago; that paling is now in quite as good a state as it was, though it is partly in the ground. It is yellow pine. Some that I put up the year before, without using Kyan’s process (yellow pine), not fixed in the ground, but close upon it, is decayed.”

This evidence, by such an experienced architect as the late Sir Robert Smirke was, is certainly of great value in favour of Kyan’s process.

The recorded evidence upon the efficiency of this mode of treating timber for its preservation is somewhat contradictory. On the Great Western Railway 40,000 loads were prepared, at an expenditure of 1¾ lb. of sublimate to each load, the timber, 7 inch, being immersed for a period of eight days, and the uniformity of the strength of the solution being constantly maintained by pumping. Some samples of this timber, after six years’ use as sleepers on the railway, were found “as sound as on the day on which they were first put down.” This timber was prepared by simple immersion only, without exhaustion or pressure. Some of the sleepers on the London and Birmingham Railway, on the other hand, which had been Kyanized three years only, were found absolutely rotten, and Kyan’s process was there consequently abandoned.

This process is said to cost an additional expense to the owner of from fifteen to twenty shillings per load of timber. Mr. Kyan at first used 1 lb. of the salt in 4 gallons of water, but it was found that the wood absorbed 4 or 5 lb. of this salt per load; more water was added to lessen the expense, until the solution became so weak as in a great measure to lose its effect.

Simple immersion being found imperfect as a means of injecting the sublimate, attempts were afterwards made to improve the efficiency of the solution by _forcing_ it into the wood. Closed tanks were substituted for the open ones, and forcing pumps, &c., were added to the apparatus. The pressure applied equalled 100 lb. on the square inch. With this arrangement a solution was made use of having 1 lb. of the sublimate to 2 gallons of water; and it was found that three-fourths of this quantity sufficed for preparing one load of timber. The timber was afterwards tested, and it was ascertained that the solution had penetrated to the heart of the logs. Mr. Thompson, the Secretary to Kyan’s Company, stated, in March, 1842, that experience had proved “that the strength of the mixture should not be less than 1 lb. of sublimate to 15 gallons of water; and he had never found any well-authenticated instance of timber decaying when it had been properly prepared at that strength.” As much as 1 in 9 was not unfrequently used. Kyan’s process is now but very rarely used; Messrs. Bethell, of King William Street, London, adopt it when requested by their customers. We have given the statements which have been made for and against this patent, but after a lapse of forty years it is difficult to reconcile conflicting statements.

Although Mr. Kyan invented his process in 1832, Sir Humphrey Davy had previously used and recommended to the Admiralty, and Navy Board, a weak solution of the same thing to be used as a wash where rot made its appearance: on giving his opinion upon Mr. Lukin’s process, that eminent chemist observed, “that he had found corrosive sublimate highly antiseptic, and preservative of animal and vegetable substances, and therefore recommended rubbing the surface of timber with a solution of it.” In 1821 Mr. Knowles, of the Navy Office, referred to the use of corrosive sublimate for timber. In fact, it was used in 1705, in Provence (France), for preserving wood from beetles. Kyan, however, was the first to apply it to any extent. In the years 1833 to 1836, at the Arsenal, Woolwich, experiments were instituted, having for their object the establishing, or otherwise, the claims of Kyan’s system; the results of which were of a satisfactory nature. Dr. Faraday has stated that the combination of the materials used was not simply mechanical but chemical; and Captain Alderson, C.E., having experimented upon some specimens of ash and Christiana deal, found that the rigidity of the timber was enhanced, but its strength was in some measure impaired; its specific gravity being also in some degree diminished.[8] Kyan’s process is said by some to render the wood brittle.

Mr. Kyan considered that the commencement of rot might be stopped or prevented by the application of corrosive sublimate, in consequence of the chemical combination which takes place between the corrosive sublimate and those albuminous particles which Berzelius and others of the highest authority consider to exist in and form the essence of wood; which, being the first parts to run to decay, cause others to decay with them. By seasoning timber in the ordinary way, the destructive principle is dried, and under common circumstances rendered inert. But when the timber is afterwards exposed to great moisture, &c. (the fermentative principle being soluble when merely dried), it will sometimes be again called into action. Kyan’s process is said not only altogether to destroy this principle and render it inert, but, by making it solid and perfectly insoluble, to remove it from the action of moisture altogether. It thus loses its hygrometric properties, and, therefore, prepared or patent seasoned timber is not liable to those changes of atmosphere which affect that which is seasoned in the common way. All woods, including mahogany and the finest and most expensive wood, may be seasoned by Kyan’s process in a very short space of time, instead of the months required by the ordinary methods.

The reader will find a great deal about Kyan’s system in the ‘Quarterly Review,’ April, 1833; and about proposals for using chloride of mercury for wood, ‘Memoirs of the Academy of Dijon,’ 1767; ‘Bull. des Sciences teen.,’ v. ii., 1824, Paris; and ‘Bull. de Pharm.,’ v. 6, 1814, Paris.

It is well known that Canadian timber is much more liable to decay than that grown in the northern parts of Europe, and for this reason is never extensively used in buildings of a superior description. The principle of decay being destroyed by Kyan’s process as above described, this objection no longer exists, and this kind of timber may therefore now be employed with as great security as that of a superior quality and higher price. The same observation applies with great force to timber of British growth, particularly to that of Scotland, much of which is considered as of little or no value for durable purposes, on account of its extreme liability to decay, whether in exposed situations or otherwise. The process invented by Kyan might therefore render of considerable value plantations of larch, firs of all kinds, birch, elm, beech, ash, poplar, &c.

Cost of process in 1832, 1_l._ per load of 50 cubic feet of timber.

Mr. W. Inwood, the architect of St. Pancras Church, London, reported favourably of Kyan’s process. On 22nd February, 1833, Professor Faraday delivered a lecture at the Royal Institution, London, on Kyanizing timber; and on 17th April, 1837, he reported that Kyan’s process had not caused any rusting or oxidation of the iron in the ship ‘Samuel Enderby,’ after the ship had been subjected to this process, and had been on a three years’ voyage to the South Sea fisheries; and in the same year, viz. 1837, Dr. Dickson delivered a lecture at the Royal Institute of British Architects on dry rot, recommending Kyan’s process.

Five years after Mr. Kyan’s invention, viz. in 1837, a Mr. Flocton invented a process for preventing decay, by saturating timber with _wood-tar_ and _acetate of iron_, but little is known of this invention: we believe it was a failure.

During the same year Mr. Flocton’s process was made known, a Frenchman named Letellier recommended saturating timber in a solution of _corrosive sublimate_, and when dry, into one of _glue_, _size_, &c.[9]

During this year Mr. Margary took out his patent for applying _sulphate of copper_ to wood. We propose to describe Margary’s process further on: we do not think he received any medals for it.

We now arrive at the modern _creosoting_ process, which was brought to perfection by the late Mr. John Bethell. Mr. Bethell’s process of creosoting, or the injection of the heavy oil of tar, was first patented by him on July 11th, 1838.[10] It consists in impregnating the wood throughout with oil of tar, and other bituminous matters containing creosote, and also with pyrolignite of iron, which holds more creosote in solution than any other watery menstruum. Creosote, now so extensively used in preserving wood, is obtained from coal tar, which, when submitted to distillation, is found to consist of pitch, essential oil (creosote), naphtha, ammonia, &c. In the application of the oil of tar for this purpose, it is now considered to be indispensable that the ammonia be got rid of; otherwise the wood sometimes becomes brown and decays, as may be constantly seen in wood coated with the common oil tar. The kind of creosote preferred by continental engineers and chemists, and also by the late Mr. John Bethell himself, is _thick_, and rich in _naphthaline_. Some English chemists now seem to prefer the thinnest oil, which contains no naphthaline, but a little more carbolic acid; the crude carbolic acid would vary from 5 to 15 per cent.: no engineer has ever required more than 5 per cent. of crude carbolic acid in creosote. The thinner oil appears to be more likely to be drawn out of the wood by the heat of the sun or absorption in powdery soil, and is more readily dissolved out by moisture.

Mummies many thousands of years old have evidently been preserved on the creosoting principle, and from observing the mummies the process of creosoting suggested itself to Mr. Bethell. The ancient Egyptians, whether from the peculiarity of their religious opinions, or from the desire to shun destruction and gain perpetuity even for their dead bodies, prepared the corpses of their deceased friends in a particular way, viz. by coagulating the albumen of the various fluids of the body by means of creosote, cedar oil, salt, and other substances, and also by excluding the air. How perfectly this method has preserved them the occasional opening of a mummy permits us to see. A good account of the operation is given in the chapter on mummies, in the second volume of Egyptian Antiquities in the ‘Library of Entertaining Knowledge.’

By the process of creosoting the timber is rendered more durable, and less liable to the attack of worms; but it becomes very inflammable; that is, _when_ once alight burns quickly; in addition to which, the disagreeable odour from timber so treated renders it objectionable for being used in the building of dwelling-houses.

The action of the solutions in water of metallic salts is, if the mixture is sufficiently strong, to coagulate the albumen in the sap; but the fibre is left unprotected.

Creosote has the same effect of coagulating the albumen, whilst it fills the pores of the wood with a bituminous asphaltic substance, which gives a waterproof covering to the fibre, prevents the absorption of water, and is obnoxious to animal life.

In cases where the complete preservation of timber is of vital importance, and expense not a consideration, the wood should be first subjected to Burnett’s process, and then creosoted; by which means it would be nearly indestructible; the reason for this combined process being, that the albumen or sap absorbs the creosote more readily than the heart of the timber, which can, however, be penetrated by the solution of chloride of zinc. Mr. John Bethell’s patent of 1853 recommends this in a rather improved form. He says the timber should _first_ be injected with metallic salts, then dried in a drying-house, then creosoted. By this method, very considerable quantities both of metallic salt and creosote can be injected into timber.

It has been stated that the elasticity of wood is increased by creosoting; the heart-wood only decays by oxidation.

The wood should be dried previous to undergoing the process, as the sapwood, otherwise almost useless, can be rendered serviceable, and for piles for marine work whole round timber should be used, because the sapwood is so much more readily saturated with the oil, and this prevents the worms from making an inroad into the heart.

Mr. Bethell uses about 10 lb. of creosote per cubic foot of wood, and he does not allow a piece of timber to be sent from his works without being tested to ascertain if it has absorbed that amount, or an amount previously agreed upon. We mention the latter statement, because it is evident that all descriptions of wood cannot be made to imbibe the same amount. This process is chiefly used for pine timber: yellow pine should absorb about 11 lb. to the cubic foot, and Riga pine about 9 lb. The quantity of oil recommended by the patentee, engineers, and others, is from 8 to 10 lb. for land purposes, and about 12 lb. to the cubic foot for marine. In this country, for marine the quantity does not exceed 12 lb.; but on the Continent, in France, Belgium, and Holland, the quantity used is from 14 to 22 lb. (!) per cubic foot. The specifications frequently issued by engineers for sleepers for foreign railways describe them to be entirely of heart-wood, and then to be creosoted to the extent of 10 lb. of the oil per cubic foot: this it is impossible to do, the value of the process being in the retention of the sapwood.

It being ascertained a few years since that the centres of some sleepers were not impregnated with the fluid, after the sleeper had been creosoted to the extent of 10 lb. of creosote per cubic foot, Sir Macdonald Stephenson suggested, as a means of obviating that defect, the boring of two holes, 1 inch in diameter, through each sleeper longitudinally, and impregnating up to 12 lb. or 14 lb. per cubic foot. By that means the creosote would be sent all through the sleeper. The boring by hand would be an expensive process, but by machinery it might be effected at a comparatively small increased cost.

During the last twenty-five years an enormous quantity of creosoted railway sleepers have been sent to India and other hot climates. The native woods are generally too hard for penetration. On the great Indian Peninsula Railway the native woods were so hard and close-grained that they could not be impregnated with any preservative substance, sál wood being principally used, into which creosote would not penetrate more than one quarter of an inch. As regards creosoting wood in India, it is moreover a costly process, owing to the difficulty and expense of conveying creosote from England; iron tanks are necessary to hold the oil when on board ship, and, being unsaleable in India, add to the expense.

English contractors often send piles to be creosoted which have been taken from the timber docks. The large quantity of water they contain resists the entrance of the oil, and the result is that a great deal of timber is badly prepared because the contractors cannot obtain it dry.

In the best creosoting works the tank or cylinder is about 6 feet diameter, and from 20 to 50 feet long. In some instances cylinders are open at both ends, and closed with iron doors, so that sleepers or timber entered at one end on being treated can be delivered finished at the opposite end; but for all practical purposes one open end is sufficient, as the oil when heated being of such a searching character it is a difficult matter to get the doors perfectly air-tight, consequently they are apt to leak during the time the pressure is being applied. Pipes are led from the cylinder to the air and force pumps; the air is not only extracted from the interior of the cylinder, but also from the pores of the timber. When a vacuum is made, the oil, which is contained in a tank below the cylinder, is allowed to rush in, and, as soon as the cylinder is full, the inlet pipe is shut and the pressure pumps started to force the oil into the wood; the pressure maintained is from 150 to 200 lb. to the square inch, until the wood has absorbed the required quantity of oil, which is learned by an index gauge fixed to the working tank below. All cylinders are fitted with safety valves, which allow the oil not immediately absorbed to pass again into the tank. The oil is heated by coils of pipe placed in the tank, through which a current of steam is passed from end to end, raising the temperature to 120°.

With regard to the cost of creosoting: half-round sleepers, being 9 feet long, 10 inches wide, and 5 inches thick, properly creosoted, are worth about 4_s._ each; adzing for the chairs (done by machine) costs 6_s._ per 100. These prices, unfortunately, vary very much, according to circumstances. The fir sleepers on the London and Birmingham Railway cost 7_s._ 6_d._ each, and the patent preservative added 9_d._ more to the expense, but they did not cost so much on other lines. A London builder wrote to us in 1870, as follows: “Our price for creosoting timber, &c., is 15_s._ per load of 50 cubic feet. Price of creosote, 2_d._ per gallon.”

By returns from the Leith Harbour Works it was shown that the average quantity of creosote absorbed by the timber was 57⅞ gallons per load, or 577 lb. weight forced into 50 cubic feet of wood. Assuming the cost to be 15_s._ per load, and the creosote at 2_d._ per gallon, the creosote would cost 9_s._ 8_d._, and the labour and profit 5_s._ 4_d._ per load of 50 cubic feet.

It is essential to observe that all methods of protecting timber depend for their success upon the skilful and conscientious manner in which they are applied; for, as they involve chemical actions on a large scale, their efficiency must depend upon the observance of the minute practical precautions required to exclude any disturbing causes. In the case of creosoting: to distil the creosote, to draw the sap or other moisture from the wood, and subsequently to inject the creosote in a proper manner, it is necessary that the operations should be carried into effect under the supervision of experienced persons of high character.

Mr. Bethell’s process has been and still is being tested on the Indian railways. According to Dr. Cleghorn, it appears that many of the creosoted sleepers have, however, “been found decayed in the centre, the interior portion being scooped out, leaving nothing but a deceptive shell, in some instances not more than ½ inch in thickness,” but he does not state whether the sleepers were prepared in England or in India; because, if prepared in India, it is probable that some of the hard Indian woods, into which it is not possible to get creosote or any other preservative fluid, had been used. Mr. Burt, who has large timber-preserving works in London for creosoting, stated about eight years since, that after an experience of twenty years, during which time he had sent over one million and a half sleepers to India alone, besides having prepared many thousand loads of timber for other purposes, he could safely assert that the instances of failure had been rare and isolated.

A section of a piece of timber impregnated with creosote presents some curious and very distinctive characteristics, according to the duration of the process of injection and amount of tar injected. In every case the injected tar follows the lines and sinuosities of the longitudinal fibres. When injected in sufficient quantity it fills the pores altogether; when, on the contrary, the process has been incompletely performed, which, however, is generally sufficient, the tar accumulates in the transverse sections, and plugs the channels that give access to deleterious agents.

The experiments made by M. Melseuns on oaken blocks exposed to the fumes of _liquid ammonia_ show that the conservating fluids follow the precise course that would be taken by decay. In wood treated with creosote the tar acts on the very parts first exposed to injury, and on the course that would be taken by decay, which is thus rendered impossible. The methods of injection suggested by M. Melseuns in 1845 did not answer equally well with every kind of wood. After trying wooden blocks in every sort of condition, dressed and in the rough, green and dry, sound and decayed, M. Melseuns found that alder, birch, beech, hornbeam, and willow were easily and completely impregnated; deal sometimes resisted the process, the innermost layers remaining white; poplar and oak offered a very great resistance--indeed, with poplar it was found necessary to repeat the process.

The decay of sleepers, prepared and unprepared, will often depend on their form. Three forms have been used: 1st, the half-round sleeper, 10 inches by 5 inches; these are now almost universally used; 2nd, the triangular sleeper, about 12 inches wide on each side, used by Mr. Cubitt on the Dover line, but since abandoned; and 3rd, the half square, 14 inches by 7 inches, used by Mr. Brunel and still in use. Mr. G. O. Maun, in reporting on the state of the sleepers of the Pernambuco Railway, states that fair average samples taken out on the 1st December, 1863 (laid in 1857), show that the half-round intermediate sleeper is in the most perfect state of preservation; in fact, nearly as good as on the day it was put down; while the square-sawn or joint sleeper has not withstood the effects of the climate so well.

The kind of ballast in which it will be most advisable to lay the sleeper is another important point to be attended to. About 12 miles of the Pernambuco Railway are entirely laid with creosoted sleepers, principally in white sand. In this description of ballast the half-round sleepers have suffered, since the opening of the first section of the line in 1858 up to 1866, a depreciation of not more than 1 per cent., whilst the square-sawn sleepers have experienced a depreciation of not less than 50 per cent. Had the latter been placed in wet cuttings with ballast retentive of moisture, no doubt the whole of them would have required to be renewed. Hence it is evident that fine open sand ballast, which allows a free drainage during the rains, is best adapted for the preservation of sleepers in the tropics: it has also been found to be the best in most countries.

The number of testimonials given in favour of creosote is very large, and are from the most eminent engineers of all countries, in addition to which Mr. Bethell has received several medals at international exhibitions. The English engineers include Messrs. Brunel, Gregory, Abernethy, Ure, Hemans, Hawkshaw, and Cudworth; the French, MM. Molinos and Forestier; the Dutch, Messrs. Waldorp, Freem, and Von Baumhauer; and the Belgian, M. Crepin. The late Mr. Brunel expressly stated that, in his opinion, well creosoted timbers would be found in a sound and serviceable condition at the expiration of forty years. M. Forestier, French engineer of La Vendée department, reporting to the juries of the French Exhibition of 1867, cites a number of experiments he has lately tried upon many pieces of creosoted and uncreosoted oak, elm, ash, Swedish, Norwegian, and Dantzic red fir, Norway white fir, plane, and poplar, and shows that in each case, except that of the poplar, the resistance of the wood both to bending and crushing weight was much increased by creosoting.

Drs. Brande, Ure, and Letheby, also bear testimony to the efficacy of this mode of preserving timber.

Creosoting has been extensively employed upon all the principal railways in Great Britain. In England, upon the London and North Western, North Eastern, South Eastern, Great Western, &c. In Scotland, on the Caledonian, Great Northern, &c. In Ireland, on the Great Southern and Western, Midland, &c. It has also been and is being employed in Belgium, Holland, France, Prussia, India, and America.

Between the years 1838 and 1840, Sir William Burnett’s (formerly Director-General of the Medical Department of the Navy) process was first made known to the public.

This process consists of an injection of _chloride of zinc_ into timber, in the proportion of about 1 lb. of the salt to about 9 or 10 gallons of water, forced into the wood under a pressure of 150 lb. per square inch.

The late Professor Graham thus wrote of its efficiency: “After making several experiments on wood prepared by the solution of chloride of zinc for the purpose of preservation, and having given the subject my best consideration, I have come to the following conclusions:

“The wood appears to be fully and deeply penetrated by the metallic salt. I have found it in the centre of a large prepared block.

“The salt, although very soluble, does not leave the wood easily when exposed to the weather, or buried in dry or damp earth. It does not come to the surface of the wood like the crystallizable salts. I have no doubt, indeed, that the greater part of the salts will remain in the wood for years, when employed for railway sleepers or such purposes. This may be of material consequence when the wood is exposed to the attacks of insects, such as the white ant in India, which, I believe, would be repelled by the poisonous metallic salt. After being long macerated in cold water, or even boiled in water, thin chips of the prepared wood retain a sensible quantity of the oxide of zinc; which I confirmed by Mr. Toplis’ test, and observed that the wood can be permanently dyed from being charged with a metallic mordant.

“I have no doubt, from repeated observations made during several years, of the valuable preservative qualities of the solution of chloride of zinc, as applied in Sir W. Burnett’s process; and would refer its beneficial action chiefly to the small quantity of the metallic salt, which is permanently retained by the ligneous fibre in all circumstances of exposure. The oxide of zinc appears to alter and harden the fibre of the wood, and destroy the solubility, and prevent the tendency to decomposition of the azotised principles it contains by entering into chemical combination with them.”

The Report of the Jury, which was drawn up by the Count of Westphalia, at the Cologne International Agricultural Exhibition, in 1865, upon prepared specimens of timber, has the following remarks on the chloride of zinc process:

1st. That chloride of zinc is the only substance which thoroughly penetrates the timber, and is at the same time the best adapted for its preservation.

2nd. That the process of impregnating the wood after cutting is more useful and rational than doing so while the tree is growing.

3rd. That red beech is the only wood which has been impregnated in an uniform and thorough manner.

It should, however, be stated that the Jury had very slender evidence presented to it respecting the creosoting process. The creosoted specimens had been impregnated under the pressure of 60 lb. to 65 lb. per square inch for three or four hours, and were consequently inefficiently done; in England the pressure per square inch would have been at least 140 lb.

Drs. Brande and Cooper, of England, and Dr. Cleghorn, of India, also wrote favourably of Sir W. Burnett’s process.

In 1847 a powerful cylinder, of Burnett’s construction, hermetically closed, was laid down adjoining the sawmills in Woolwich dockyard. It was found to admit the largest description of timber for the purpose of having the moisture extracted, and the pores filled with chloride of zinc. Three specimens of wood--English oak, English elm, and Dantzic fir--remained uninjured in the fungus pit at Woolwich for five years; while similar, but unprepared, specimens were all found more or less decayed.

The cost of preparing timber by this process is 12_s._ per load, besides 2_s._ for landing and loading: 1 lb. of the material costing 1_s._, which is sufficient for 9 or 10 gallons of water.

Sir W. Burnett and Co.’s works for hydraulic apparatus and tanks are at Nelson Wharf, Millwall, Poplar; their office is at 90, Cannon Street, London. Their terms are--

“For timber, round or square, including planks, deals, hop-poles, paving-blocks, &c., against rot, 12_s._ per load of 50 cubic feet.

“For park palings, cabinet work, wine and other laths, as per agreement.

“For railway sleepers, 9 feet long, 10 inches by 5 inches, landing and reshipping included, 7_d._ each.

“For timber to be rendered uninflammable, 25_s._ per load.”

Sir W. Burnett’s firm now sell their patent concentrated solution at 5_s._ per gallon: each gallon must be diluted with 40 gallons of water, according to the instructions in the licence, for which no charge is made.

The reader will probably have observed that this process is _considered_ to render timber uninflammable; then let us see what will be the cost of obtaining a fire-proof house.

The principal building material which causes the destruction of our houses by fire is wood--_combustible wood_. If, therefore, (as nearly all our houses are “brick and timber” erections,) we render this wood uninflammable, what will the cost be?

The following is an _approximate_ estimate of the extra expense, including sundries, &c.:--

Timber and Deals. Cost of House. Additional expense. Loads. £ £

25 1000 34

15 600 21

10 400 14

8 250 12

When will the Building Act compel us to use this table _in daily practice?_

Although among the many attempts to preserve wood those in England have proved the most successful, it should be mentioned that France, Germany, and America have given much attention to the subject.

At the end of the last century Du Hamel and Buffon pointed out the possibility of preserving wood, as well as the means of rendering it unalterable. As early as 1758 Du Hamel made experiments on the vital suction of plants, and made some curious observations on the different rings of vegetable matter which absorb most liquid in different plants. He also tried the effect of vital suction and pressure (of gravitation) acting at the same time. His process was reviewed by Barral in 1842.

About 1784 M. Migneron invented a process about which little is now known, but the wood was covered with certain fatty substances. Wood nine years exposed to deterioration was improved by this process. M. Migneron had the approval of Buffon, Franklin, and the Academies. His invention was again brought into notice in 1807, when it was found that timber which had been prepared by it in 1784, and exposed more than twenty years, was quite sound.

In 1811 Cadet de Gassicourt made different kinds of wood imbibe vegetable and mineral substances, and certain unguents: he used metallic salts (iron, tin, &c.).

In 1813 M. Champy plunged wood into a bath of _tallow_ at 334°, and kept it there two or three hours. His experiments were afterwards repeated by Mr. Payne.

About the year 1832 it was proposed in America to apply _pyroligneous acid_ to the surface of wood, or introduce it by fumigation.

Biot (who has written an excellent life of Sir Isaac Newton) remarked, in 1831, that wood could be soaked by pressure; but his process of penetrating it with liquids was imperfect, and his discovery remains unapplied.

A Frenchman, of the name of Bréant, made about this time a discovery which preceded Boucherie’s method, which is adopted to a great extent in France. Bréant’s apparatus consisted of a very ingenious machine, which, acting by pressure, caused liquids to penetrate to all points of a mass of wood of great diameter and considerable length. He may therefore be regarded as having solved the problem of penetration in a scientific, though not in a practically applied, point of view. Dr. Boucherie testified before the Académie des Sciences, in 1840, to the merit of Bréant’s invention, which, with modifications by Payne, Brochard, and Gemini, has been worked in France and England. This process was recommended by Payne in 1840 and 1844, and imitated by him in France, and later on by Yengat and Bauner, who used both _an air pump and a forcing pump_. Bréant obtained three patents, viz. 1st, in 1831, to act by pressure; 2nd, in 1837, by vital suction: and 3rd, in 1838, vacuum by steam. A mixture of linseed oil and resin succeeded best with him. He attached more importance to the thorough penetration of the wood than to the choice of the penetrating substances. He borrowed his process from Du Hamel, but to make the necessary suction in the pores he produces a partial vacuum in the impregnating cylinder by filling it with steam, and condensing the steam.

Previous to Boucherie’s method, a German, Frantz Moll, in 1835, proposed to introduce into wood _creosote in a state of vapour_, but the process was found to be too expensive. This was a modification of Maconochie and Lukin’s trials in 1805 and 1811.[11] A similar process has since arisen in New York: we believe Mr. Renwick, of that place, suggested it.

Such were the known labours, when Dr. Boucherie, in December, 1837, devoted his time to a series of experiments upon timber, with a view to discover some preservative process which should answer the following requirements: First, for protecting wood from dry rot or wet rot; second, for increasing its hardness; third, for preserving and developing its flexibility and elasticity; fourth, for preventing its decay, and the fissures that result from it, when, after having been used in construction, it is left exposed to the variations of the atmosphere; fifth, for giving it various and enduring colours and odours; and sixth and last, for greatly reducing its inflammability.

It is a curious coincidence that at Bordeaux, in 1733, the Academy received a memoir relative to the circulation of the sap and coloured liquids in plants; and it was at Bordeaux, a century afterwards, viz. 1837, that M. Boucherie first mentioned his method.

M. Boucherie’s process was first discussed in Paris in June, 1840. It consists in causing a solution of _sulphate of copper_ to penetrate to the interior of freshly cut woods, to preserve them from decay; he occasionally used the chloride of calcium, the _pyrolignite of iron_ (_pyrolignite brut de fer_), _prussiate of iron_, _prussiate of copper_, and various other metallic salts. As a general rule sulphate of copper is used; but when the hardness of the wood is desired to be increased, pyrolignite of iron is taken (1 gallon of iron to 6 gallons of water); and when the object is to render the wood flexible, elastic, and at the same time uninflammable, chloride of calcium is used. The liquid is taken up by the tree either whilst growing in the earth or immediately after it has been felled. Not more than two or three months should be allowed to elapse before the timber is operated upon, but the sooner it undergoes the process after being felled the better.

Sulphate of copper is said to be superior to corrosive sublimate. Dr. Boucherie’s process of the injection of wood with the salts of copper is as simple as it is easy. For those woods intended for poles it consists in plunging the base of a branch, furnished with leaves, into a tub containing the solution. The liquid ascends into the branches by the action of the leaves, and the wood is impregnated with the preservative salt. As for logs, the operation consists in cutting down the tree to be operated upon; fixing at its base a plank, which is fixed by means of a screw placed in the centre, and which can be tightened at will when placed in the centre of the tree. This plank has, on the side to be applied to the bottom of the tree, a rather thick shield of leather, cloth, pasteboard, or some other substance, intended to establish a space between it and the wood, sufficient for the preserving fluid to keep in contact with the freshly cut surface of the tree. The liquid is brought there from a tub or other reservoir, by the help of a slanting pole made on the upper surface of the tree, and in which is put a tube, adapted at its other extremity to a spigot in the upper reservoir which contains the solution. A pressure of 5 mètres suffices; so that the instant the sap of the tree is drawn away it escapes, and is replaced by the liquid saturated with sulphate of copper. The proportion of sulphate of copper in the solution should be 1 lb. of the salt to 12½ gallons of water. As soon as the operation terminates (and it lasts for some hours for the most difficult logs), the wood is ready for use.

For various practical reasons, the first invention of impregnating the wood of the tree whilst still in a growing state, causing it to suck up various solutions by means of the absorbing power of the leaves themselves, was subsequently abandoned; and at the present time a cheap, simple, and effective process is adopted for impregnating the felled timbers with the preserving liquid, designated in France “trait de scie, et la cuisse foulante.” The trunk of a newly felled tree is cut into a length suitable for two railway sleepers; a cross cut is made on the prostrate timber to nearly nine-tenths of its diameter; a wedge is then inserted, and a cord is wound round on the cut surface, leaving a shallow chamber in the centre, when it is then closed by withdrawing the wedge. A tube is then inserted through an auger hole into this chamber, and to this tube is attached an elastic connecting tube from a reservoir placed some 20 or 30 feet above the level on which the wood lies, and a stream of the saturating fluid with this pressure passes into the chamber, presses on the sap in the sap tubes, expels it at each end of the tree, and itself supplies its place. The fluid used is a solution of copper in water, in the proportion of 10 or 12 per cent., and a chemical test that ascertains the pressure of the copper solution is applied at each end of the tree from which the sap exudes, by which the operator ascertains when the process is completed.

A full account of this process may be found in the number for June, 1840, of ‘Les Annales de Chimie et de Physique.’ Messrs. de Mirbel, Arago, Poucelet, Andouin, Gambey, Boussingault, and Dumas, on the part of l’Académie des Sciences, made a report upon Dr. Boucherie’s process, confirming the value of the invention. In France, Dr. Boucherie, some years since, relinquished his brévet, and threw the process open to the public, in consideration of a national reward; whilst in England he has obtained two patents (1838 and 1841), which, however, are similar to Bethell’s patent, obtained by him on July 11, 1838: _which is the same day and year of Boucherie’s patent_. A prize medal was awarded for Dr. Boucherie’s process at the Great Exhibition in London, in 1851, and a grande médaille d’honneur, at the Paris Exhibition of 1855. Many thousands of railway sleepers have been prepared by this process, and laid down on the Great Northern Railway of France, and are at present perfectly sound, whilst others not prepared, on the same line, have rotted. Boucherie’s process was used on Belgium railways up to 1859; and it is to be regretted that the reasons which led to its abandonment have not been given in the reports of the railway administration, as such reasons would have afforded reliable data for future experimentalists to go upon.

Messrs. Légé and Fleury-Pironnet’s patent for the injection of sulphate of copper into beech and poplar is as follows: After the wood is placed, and the opening hermetically sealed, a jet of steam is introduced, intended at first to enter the timber and open its pores for the purpose of obtaining a sudden vacuum, so as to establish at any time a communication between the interior of the cylinder and the cold water condenser; at the same time the air pump is put in action. The vacuum caused is very powerful, and is equal to 25½ ins. of the barometer. Under the double influence of the heat and the vacuum the sap is quickly evaporated from the wood as steam, and ejected from the cylinder by the air pump, so that in a very short time the wood is fully prepared to admit the preserving liquid through the entire bulk.

The use of sulphate of copper for preserving timber has not been, however, confined to France, for about the time Dr. Boucherie brought forward his process, a Mr. Margary took out a patent in England for the use of the same material. His method consists in steeping the substances to be preserved in a solution of sulphate of copper, of the strength of 1 lb. of the sulphate to 8 gallons of water, and leaving them in it till thoroughly saturated. The timber is allowed to remain in the tank two days for every inch of its thickness. Another method is to place the timber in a closed iron vessel of great strength, and it is made to imbibe the solution by exhaustion and pressure, the operation occupying but a short time.

Sulphate of copper is sold in quantities at 4_d._ per lb.; so that 100_l._ would buy 6000 lb., and each pound weight is sufficient for 7 or 8 gallons of water, according to Margary; or 12 gallons of water, according to Boucherie.

To preserve railway sleepers, the French railway engineers require ¼ lb. of sulphate of copper per cubic foot, say at least 12 lbs. to the load of 50 feet, to be used in a 2 per cent. solution; so that a load of timber can be rendered imperishable for the sum of four shillings, exclusive of labour, if sulphate of copper be reckoned at 4_d._ per lb.

With respect to the use of pyrolignite of iron, Mr. Bethell considers it an expensive process, the pyrolignite costing 6_d._ to 9_d._ per gallon, whilst the oil of tar can be delivered at from 2_d._ to 3_d._ per gallon: the cost of these materials is constantly varying.

A great many sleepers were prepared on the Great Western Railway by pyrolignite of iron, and all have _decayed_. Their black colour makes them exactly resemble creosoted sleepers, and _many mistakes_ have arisen from this resemblance.

Messrs. Dorsett and Blythé’s (of Bordeaux) patent process of preparing wood by the injection of heated solutions of sulphate of copper is said to have been adopted by French, Spanish, and Italian, as well as other continental railway companies, by the French Government for their navy and other constructions, and by telegraph companies for poles on continental lines. It is as cheap as creosote, and is employed in places where creosote cannot be had. Wood prepared by it is rendered incombustible. Wood for outdoor purposes so prepared has a clean yellowish surface, without odour; it requires no painting, remains unchangeable for any length of time, and can be employed for any purpose, the same as unprepared material, and carried with other cargo without hindrance.[12] Messrs. Dorsett and Blythé’s process is similar to that of Mr. Knab, which consisted of a solution of sulphate of copper, heated to nearly boiling point, and placed in a lead cylinder, protected by wood.

In 1846, 80,000 sleepers, treated with sulphate of copper, were laid down on French railways, and after nine years’ exposure were found to be as perfect as when first laid.

Mr. H. W. Lewis, University of Michigan, U.S., thus writes in the ‘Journal’ of the Franklin Institute, in 1866, with reference to the decay of American railway sleepers: “Allowing 2112 sleepers per mile, at 50 cents each, 1056 dols. per mile of American railroad decay every seven years. Thoroughly impregnate those sleepers with sulphate of copper, at a cost of 5 cents each, and they would last twice as long. Thus would be effected a saving of 880 dols. per mile in the seven years on sleepers alone. In the United States, there are 33,906·6 miles of railroad. The whole saving on these lines would be 29,389,568 dols., or upwards of 4,262,795 dols. per annum.”

With reference to the decay of unprepared wooden sleepers, it may be here stated that the renewal of wooden sleepers on the Calcutta and Delhi Indian line alone costs annually 130,000_l._

The preservative action of sulphate of copper on wood has long been known, but there are several things in its action which require explanation. The ‘London Review’ says that Kœnig has lately investigated the chemical reactions which occur when wood is impregnated with a preservative solution of blue vitriol. He finds, as a general rule, that a certain quantity of basic sulphate of copper remains combined in the pores of the wood in such a manner that it cannot be washed out with water. The copper salt may be seen by its green colour in the spaces between the yearly rings in the less compact portions of the wood, that is to say, in those portions which contain the sap. Those varieties of wood which contain the most resin retain the largest amount of the copper salt--oak, for example, retaining but little of it. The ligneous fibre itself appears to have little or nothing to do with the fluxation of the copper salt, and indeed none whatever is retained in chemical combination, so that it cannot be washed out with water, by pure cellulose. When wood, from which all resin has been extracted by boiling alcohol, is impregnated with sulphate of copper, it does not become coloured like the original resinous wood, and the copper salt contained in it may be readily washed out with water. In like manner, from impregnated resinous wood all the copper salt may be removed, with the resin, by means of alcohol. The constituents of the blue vitriol are consequently fixed in the wood by means of the resin which this contains. Further, it is found that the impregnated wood contains less nitrogen than that which is unimpregnated, and that it is even possible to remove all the nitrogenous components of the wood by long-continued treatment with the solution of sulphate of copper; the nitrogenous matters being soluble in an excess of this solution, just as the precipitate which forms when aqueous solutions of albumen and sulphate of copper are mixed is soluble in excess of the latter. Since the nitrogenous matters are well known to be promoters of putrefaction, their removal readily accounts for the increased durability of the impregnated wood. The utility of blue vitriol as a preservative may also depend on a measure upon the resinous copper salt which is formed, by which the pores of the wood are more or less filled up, and the ligneous fibre covered, so that contact with the air is prevented, and the attack of insects hindered. It is suggested that those cases in which the anticipated benefits have not been realized in practice, by impregnating wood with a solution of blue vitriol, may probably be referred to the use of an insufficient amount of this agent; that is, where the wood was not immersed in the solution for a sufficient length of time. The action should be one of lixiviation, not merely of absorption.

In 1841, a German, named Müenzing, a chemist of Heibronn, proposed _chloride of manganese_ (waste liquor in the manufacture of bleaching powder) as a preservative against dry rot in timber; but his process has not been adopted in England, and very little noticed abroad.

In July, 1841, Mr. Payne patented his invention for _sulphate of iron_ in London; and in June and November, 1846, in France; and in 1846 in London, for _carbonate of soda_.[13] The materials employed in Payne’s process are sulphate of iron and sulphate of lime, both being held in solution with water. The timber is placed in a cylinder in which a vacuum is formed by the condensation of steam, assisted by air pumps; a solution of sulphate of iron is then admitted into the vessel, which instantly insinuates itself into all the pores of the wood, previously freed from air by the vacuum, and, after about a minute’s exposure, impregnates its entire substance; the _sulphate of iron_ is then withdrawn, and another solution of _sulphate of lime_ thrown in, which enters the substance of the wood in the same manner as the former solution, and the two salts react upon each other, and form two new combinations within the substance of the wood--muriate of iron, and muriate of lime. One of the most valuable properties of timber thus prepared is its perfect incombustibility: when exposed to the action of flame or strong heat, it simply smoulders, and emits no flame. We may also reasonably infer that with such a compound in its pores, decay must be greatly retarded, and the liability to worms lessened, if not prevented. The greatest drawback consists in the increased difficulty of working. This invention has been approved by the Commissioners of Woods and Forests, and has received much approbation from the architectural profession. Mr. Hawkshaw, C.E., considers that this process renders wood brittle. It was employed for rendering wood uninflammable in the Houses of Parliament (we presume, in the carcase; for _steaming_ was used for the joiner’s work), British Museum, and other public buildings; and also for the Royal Stables at Claremont.

In 1842, Mr. Bethell stated before the Institute of Civil Engineers, London, that _silicate of potash_, or _soluble glass_, rendered wood uninflammable.

In 1842, Professor Brande proposed _corrosive sublimate_ in _turpentine_, or _oil of tar_, as a preservative solution.

In 1845, Mr. Ransome suggested the application of _silicate of soda_, to be afterwards decomposed by an acid in the fibre of the wood; and in 1846, Mr Payne proposed soluble sulphides of the earth (_barium sulphide_, &c.), to be also afterwards decomposed in the woods by acids.

In 1855, a writer in the ‘Builder’ suggested an equal mixture of alum and borax (biborate of soda) to be used for making wood uninflammable. We have no objection to the use of alum and borax to render wood uninflammable, providing it does not _hurt the wood_.

Such are the _principal_ patents, suggestions, and inventions, up to the year 1856; but there are many more which have been brought before the public, some of which we will now describe.

Dr. Darwin, some years since, proposed absorption, first, of _lime water_, then of a weak solution of _sulphuric acid_, drying between the two, so as to form a gypsum (sulphate of lime) in the pores of the wood, the latter to be previously well seasoned, and when prepared to be used in a dry situation.

Dr. Parry has recommended a preparation composed of _bees-wax_, _roll brimstone_, and _oil_, in the proportion of 1, 2, and 3 ounces to ¾ gallon of water; to be boiled together and laid on hot.

Mr. Pritchard, C.E., of Shoreham, succeeded in establishing _pyrolignite of iron_ and _oil of tar_ as a preventive of dry rot; the pyrolignite to be used very pure, the oil applied afterwards, and to be perfectly free from any particle of ammonia.

Mr. Toplis recommends the introduction into the pores of the timber of a solution of sulphate or muriate of iron; the solution may be in the proportion of about 2 lb. of the salt to 4 or 5 gallons of water.

An invention has been lately patented by Mr. John Cullen, of the North London Railway, Bow, for preserving wood from decay. The inventor proposes to use a composition of _coal-tar_, _lime_, and _charcoal_; the charcoal to be reduced to a fine powder, and also the lime. These materials to be well mixed, and subjected to heat, and the wood immersed therein. The impregnation of the wood with the composition may be materially aided by means of exhaustion and pressure. Wood thus prepared is considered to be proof against the attacks of the white ant.

The process of preserving wood from decay invented by Mr. L. S. Robins, of New York, was proposed to be worked extensively by the “British Patent Wood Preserving Company.” It consists in first removing the surface moisture, and then charging and saturating the wood with hot _oleaginous vapours_ and compounds. As the Robins’ process applies the preserving material in the form of vapour, the wood is left clean, and after a few hours’ exposure to the air it is said to be fit to be handled for any purposes in which elegant workmanship is required. Neither science nor extraordinary skill is required in conducting the process, and the treatment under the patent is said to involve only a trifling expense.

Reference has already been made to the use of _petroleum_. The almost unlimited supply of it within the last few years has opened out a new and almost boundless source of wealth. An invention has been patented in the name of Mr. A. Prince, which purports to be an improvement in the mode of preserving timber by the aid of petroleum. The invention consists, firstly, in the immersion of the timber in a suitable vessel or receptacle, and to exhaust the air therefrom, by the ordinary means of preserving wood by saturation. The crude petroleum is next conveyed into the vessel, and thereby caused to penetrate into every pore or interstice of the woody fibre, the effect being, it is said, to thoroughly preserve the wood from decay. He also proposes to mix any cheap mineral paint or pigment with crude petroleum to be used as a coating for the bottom of ships before the application of the sheathing, and also to all timber for building or other purposes. The composition is considered to render the timber indestructible, and to repel the attacks of insects. Without expressing any opinion upon this patent as applied to wood for building purposes, we must again draw attention to the high inflammability of petroleum.

The ‘Journal’ of the Board of Arts and Manufactures for Upper Canada considers the following to be the cheapest and the best mode of preserving timber in Canada: Let the timbers be placed in a drying chamber for a few hours, where they would be exposed to a temperature of about 200°, so as to drive out all moisture, and by heat, coagulate the albuminous substance, which is so productive of decay. Immediately upon being taken out of the drying chamber, they should be thrown into a tank containing crude petroleum. As the wood cools, the air in the pores will contract, and the petroleum occupy the place it filled. Such is the extraordinary attraction shown by this substance for dry surfaces, that by the process called capillary attraction, it would gradually find its way into the interior of the largest pieces of timber, and effectually coat the walls and cells, and interstitial spaces. During the lapse of time, the petroleum would absorb oxygen, and become inspissated, and finally converted into a bituminous substance, which would effectually shield the wood from destruction by the ordinary processes of decay. The process commends itself on account of its cheapness. A drying chamber might easily be constructed of sheet iron properly strengthened, and petroleum is very abundant and accessible. Immediately after the pieces of timber have been taken out of the petroleum vat, they should be sprinkled with wood ashes in order that a coating of this substance may adhere to the surface, and carbonate of potash be absorbed to a small depth. The object of this is to render the surface incombustible; and dusting with wood ashes until quite dry will destroy this property to a certain extent.

The woodwork of farm buildings in this country is sometimes subjected to the following: Take two parts of _gas-tar_, one part of _pitch_, one part _half caustic lime_ and _half common resin_; mix and boil these well together, and put them on the wood quite hot. Apply two or three coats, and while the last coat is still warm, dash on it a quantity of well-washed sharp sand, previously prepared by being sifted through a sieve. The surface of the wood will then have a complete stone appearance, and may be durable. It is, of course, necessary, that the wood be perfectly dry, and one coat should be well hardened before the next is put on. It is necessary, by the use of lime and long boiling, to get quit of the ammonia of the tar, as it is considered to injure the wood.

Mr. Abel, the eminent chemist to the War Department, recommends the application of _silicate of soda_ in solution, for giving to wood, when applied to it like paint, a hard coating, which is durable for several years, and is also a considerable protection against fire. The silicate of soda, which is prepared for use in the form of a thick syrup, is diluted in water in the proportion of 1 part by measure of the syrup to 4 parts of water, which is added slowly, until a perfect mixture is obtained by constant stirring. The wood is then washed over _two_ or _three_ times with this liquid by means of an ordinary whitewash brush, so as to absorb as much of it as possible. When this first coating is nearly dry, the wood is painted over with _another_ wash made by slaking good fat lime, diluted to the consistency of thick cream. Then, after the limewash has become moderately dry, _another_ solution of the silicate of soda, in the proportion of 1 of soda to 2 of water, is applied in the same manner as the first coating. The preparation of the wood is then complete; but if the lime coating has been applied too quickly, the surface of the wood may be found, when quite dry, after the last coating of the silicate, to give off a little lime when rubbed with the hand; in which case it should be _once more_ coated over with a solution of the silicate of the same strength as in the first operation. If Mr. Abel had been an architect or builder, he would never have invented this process. What would the cost be? and would not a special clerk of the works be necessary to carry out this method in practice?

The following coating for piles and posts, to prevent them from rotting, has been recommended on account of its being economical, impermeable to water, and nearly as hard as stone: Take 50 parts of _resin_, 40 of _finely powdered chalk_, 300 parts of _fine white sharp sand_, 4 parts of _linseed oil_, 1 part of native _red oxide of copper_, and 1 part of _sulphuric acid_. First, heat the resin, chalk, sand, and oil, in an iron boiler; then add the oxide, and, with care, the acid; stir the composition carefully, and apply the coat while it is still hot. If it be not liquid enough, add a little more oil. This coating, when it is cold and dry, forms a varnish which is as hard as stone.

Another method for fencing, gate-posts, garden stakes, and timber which is to be buried in the earth, may be mentioned. Take 11 lb. of _blue vitriol_ (sulphate of copper) and 20 quarts of water; dissolve the vitriol with boiling water, and then add the remainder of the water. The end of the wood is then to be put into the solution, and left to stand four or five days; for shingle, three days will answer, and for posts, 6 inches square, ten days, Care should be taken that the saturation takes place in a well-pitched tank or keyed box, for the reason that any barrel will be shrunk by the operation so as to leak. Instead of expanding an old cask, as other liquids do, this shrinks it. This solution has also been used in dry rot cases, when the wood is only slightly affected.

It will sometimes be found that when oak fencing is put up new, and tarred or painted, a fungus will vegetate through the dressing, and the interior of the wood be rapidly destroyed; but when undressed it seems that the weather desiccates the gum or sap, and leaves only the woody fibre, and the fence lasts for many years.

About fifteen years ago, Professor Crace Calvert, F.R.S., made an investigation for the Admiralty, of the qualities of different woods used in ship-building. He found the goodness of teak to consist in the fact that it is highly charged with _caoutchouc_; and he considered that if the tannin be soaked out of a block of oak, it may then be interpenetrated by a _solution of caoutchouc_, and thereby rendered as lasting as teak.

We can only spare the space for a few words about this method.

1st. We have seen lead which has formed part of the gutter of a building previous to its being burnt down: lead melts at 612° F.; caoutchouc at 248° F.; therefore caoutchouc would not prevent wood from being destroyed by fire. At 248° caoutchouc is highly inflammable, burns with a white flame and much smoke.

2nd. We are informed by a surgical bandage-maker of high repute, that caoutchouc, when used in elastic kneecaps, &c., _will perish_, if the articles are left in a drawer for two or three years. When hard, caoutchouc is brittle.

Would it be advisable to interpenetrate oak with a solution of caoutchouc? In 1825, Mr. Hancock proposed a solution of 1½ lb. of caoutchouc in 3 lb. of essential oil, to which was to be added 9 lb. of tar. Mr. Parkes, in 1843, and M. Passez, in 1845, proposed to dissolve caoutchouc in sulphur: painting or immersing the wood. Maconochie, in 1805, after his return from India, proposed distilled _teak_ chips to be injected into fir woods.

Although England has been active in endeavouring to discover the best and cheapest remedy for dry rot, France has also been active in the same direction.

M. le Comte de Chassloup Lambat, Member of the late Imperial Senate of France, considers that, as _sulphur_ is most prejudicial to all species of fungi, there might, perhaps, be some means of making it serviceable in the preservation of timber. We know with what success it is used in medicine. It is also known that coopers burn a sulphur match in old casks before using them--a practice which has evidently for its object the prevention of mustiness, often microscopic, which would impart a bad flavour to the wine.

M. de Lapparent, late Inspector-General of Timber for the French Navy, proposed to prevent the growth of fungi by the use of a paint having flour of sulphur as a basis, and linseed oil as an amalgamater. In 1862 he proposed charring wood; we have referred to this process in our last chapter (p. 96).

The paint was to be composed of:

Flour of sulphur 200 grammes 3,088 grains. Common linseed oil 135 ” 2,084 ” Prepared oil of manganese 30 ” 463 ”

He considered that by smearing here and there either the surfaces of the ribs of a ship, or below the ceiling, with this paint, a slightly sulphurous atmosphere will be developed in the hold, which will purify the air by destroying, at least in part, the sporules of the fungi. He has since stated that his anticipations have been fully realized. M. de Lapparent also proposes to prevent the decay of timber by subjecting it to a skilful carbonization with common inflammable coal gas. An experiment was made at Cherbourg, which was stated to be completely successful. The cost is only about 10 cents per square yard of framing and planking.[14] M. de Lapparent’s gas method is useful for burning off old paint. We saw it in practice (April, 1875) at Waterloo Railway Station, London, and it appeared to be effective.

At the suggestion of MM. Le Châtelier (Engineer-in-chief of mines) and Flachat, C.E.’s, M. Ranee, a few years since, injected in a Légé and Fleury cylinder certain pieces of white fir, red fir, and pitch pine with _chloride of sodium_, which had been deprived of the manganesian salts it contained, to destroy its deliquescent property. Some pieces were injected four times, but the greatest amount of solution injected into pitch pine heart-wood was from 3 to 4 per cent., and very little more was injected into the white and red fir heart-wood. It was also noticed that sapwood, after being injected four times, only gained 8 per cent. in weight in the last three operations. The experiments made to test the relative incombustibility of the injected wood showed that the process was a complete failure; the prepared wood burning as quickly as the unprepared wood.

M. Paschal le Gros, of Paris, has patented his system for preserving all kinds of wood, by means of a _double salt of manganese_ and of _zinc_, used either alone or with an admixture of _creosote_. The solution, obtained in either of the two ways, is poured into a trough, and the immersion of the logs or pieces of wood is effected by placing them vertically in the trough in such a manner that they are steeped in the liquid to about three-quarters of their length. The wood is thus subjected to the action of the solution during a length of time varying from twelve to forty-eight hours. The solution rises in the fibres of the wood, and impregnates them by the capillary force alone, without requiring any mechanical action. The timber is said to become incombustible, hard, and very lasting.

M. Fontenay, C.E., in 1832, proposed to act upon the wood with what he designated _metallic soap_, which could be obtained from the residue in greasing boxes of carriages; also from the acid remains of _oil_, _suet_, _iron_, and _brass dust_; all being melted together. In 1816 Chapman tried experiments with _yellow soap_; but to render it sufficiently fluid it required forty times its weight of water, in which the quantity of resinous matter and tallow would scarcely exceed ⅟80th; therefore no greater portion of these substances could be left in the pores of the wood, which could produce little effect.

M. Letellier, in 1837, proposed to use _deuto-chloride of mercury_ as a preservative for wood.

M. Dondeine’s process was formerly used in France and Germany. It is a paint, consisting of many ingredients, the principal being _linseed oil, resin, white lead, vermilion, lard, and oxide of iron_. All these are to be well mixed, and reduced by boiling to one-tenth, and then applied with a brush. If applied cold, a little varnish or turpentine to be added.

Little is known in England of the inventions which have arisen in foreign countries not already mentioned.

M. Szerelmey, a Hungarian, proposed, in 1868, _potassa_, _lime_, _sulphuric acid_, _petroleum_, &c., to preserve wood.

In Germany, the following method is sometimes used for the preservation of wood: Mix 40 parts of _chalk_, 40 parts of _resin_, 4 of _linseed oil_; melting them together in an iron pot; then add 1 part of native _oxide of copper_, and afterwards, carefully, 1 part of _sulphuric acid_. The mixture is applied while hot to the wood by means of a brush, and it soon becomes very hard.[15]

Mr. Cobley, of Meerholz, Hesse, has patented the following preparation. A strong solution of _potash_, _baryta_, _lime_, _strontia_, or any of their salts, are forced into the pores of timber in a close iron vessel by a pump. After this operation, the liquid is run off from the timber, and _hydro-fluo-silicic acid_ is forced in, which, uniting with the salts in the timber, forms an insoluble compound capable of rendering the wood uninflammable.

About the year 1800, Neils Nystrom, chemist, Norkopping, recommended a solution of _sea salt and copperas_, to be laid upon timber as hot as possible, to prevent rottenness or combustion. He also proposed a solution of _sulphate of iron_, _potash_, _alum_, &c., to extinguish fires.

M. Louis Vernet, Buenos Ayres, proposed to preserve timber from fire by the use of the following mixture: Take 1 lb. of _arsenic_, 6 lb. of _alum_, and 10 lb. of _potash_, in 40 gallons of water, and mix with _oil_, or any suitable tarry matters, and paint the timber with the solution. We have already referred to the conflicting evidence respecting alum and water for wood: we can now state that Chapman’s experiments proved that _arsenic_ afforded no protection against dry rot. Experiments in Cornwall have proved that where arsenical ores have lain on the ground, vegetation will ensue in two or three years after removal of the ore. If, therefore, alum or arsenic have no good effect on timber with respect to the dry rot, we think the use of both of them together would certainly be objectionable.

The last we intend referring to is a composition frequently used in China, for preserving wood. Many buildings in the capital are painted with it. It is called _Schoicao_, and is made with 3 parts of blood deprived of its febrine, 4 parts of lime and a little alum, and 2 parts of liquid silicate of soda. It is sometimes used in Japan.

It would be practically useless to quote any further remedies, and the reader is recommended to carefully study those quoted in this chapter, and of their utility to judge for himself, bearing in mind those principles which we have referred to before commencing to describe the patent processes. A large number of patents have been taken out in England for the preservation of wood by preservative processes, but only two are now in use,--that is, to any extent,--viz. Bethell’s and Burnett’s. Messrs. Bethell and Co. now impregnate timber with _copper, zinc, corrosive sublimate, or creosote_; the four best patents.

We insert here a short analysis of different _methods_ proposed for seasoning timber:--

Vacuum and Pressure Processes generally.

Bréant’s. Bethell’s. Payne’s. Perin’s. Tissier’s.

Vacuum by Condensation of Steam.

Tissier. Bréant. Payne. Renard Perin, 1848. Brochard and Watteau, 1847.

Separate Condenser.

Tissier.

Employ Sulphate of Copper in closed vessels.

Bethell’s Patent, 11th July, 1838. Tissier, 22nd October, 1844. Molin’s Paper, 1853. Payen’s Pamphlet. Légé and Fleury’s Pamphlet.

Current of Steam.

Moll’s Patent, 19th January, 1835. Tissier’s ” 22nd October, 1844. Payne’s ” 14th Nov., 1846. Meyer d’Uslaw, 2nd January, 1851. Payen’s Pamphlet.

Hot Solution.

Tissier’s Patent, 22nd October, 1844. Knab’s Patent, 8th September, 1846.

Most solutions used are heated.

The following are the chief _ingredients_ which have been recommended, and some of them tried, to prevent the decomposition of timber, and the growth of fungi:--

Acid, Sulphuric. ” Vitriolic. ” of Tar. Carbonate of Potash. ” Soda. ” Barytes. Sulphate of Copper. ” Iron. ” Zinc. ” Lime. ” Magnesia. ” Barytes. ” Alumina. ” Soda. Salt, Neutral. Salt, Selenites. Oil, Vegetable. ” Animal. ” Mineral. Muriate of Soda. Marcosites, Mundic. ” Barytes. Nitrate of Potash. Animal Glue. ” Wax. Quick Lime. Resins of different kinds. Sublimate, Corrosive. Peat Moss.

For the _non-professional_ reader we find we have _three_ facts:

1st. The most successful patentees have been Bethell and Burnett, in England; and Boucherie, in France: all B’s.

2nd. The most successful patents have been _knighted_. Payne’s patent was, we believe, used by Sirs R. Smirke and C. Barry; Kyan’s, by Sir R. Smirke; Burnett’s, by Sirs M. Peto, P. Roney, and H. Dryden; while Bethell’s patent can claim Sir I. Brunel, and many other knights. We believe Dr. Boucherie received the Legion of Honour in France.

3rd. There are only at the present time three timber-preserving works in London, and they are owned by Messrs. Bethell and Co., Sir F. Burnett and Co., and Messrs. Burt, Boulton, and Co.: all names commencing with the letter B.

For the _professional_ reader we find we have _three hard_ facts:

The most successful patents may be placed in three classes, and we give the key-note of their success.

1st. ONE MATERIAL AND ONE APPLICATION.--Creosote, Petroleum. _Order_--Ancient Egyptians, or Bethell’s, Burmese.

2nd. TWO MATERIALS AND ONE APPLICATION.--Chloride of zinc and water; sulphate of copper and water; corrosive sublimate and water. _Order_--Burnett, Boucherie, Kyan.

3rd. TWO MATERIALS AND TWO APPLICATIONS.--Sulphate of iron and water; afterwards sulphate of lime and water. Payne.

We thus observe there are _twice three_ successful patent processes.

Any inventions which cannot be brought under these three classes have had a short life; at least, we think so.

The same remarks will apply to _external_ applications for wood--for instance, coal-tar, _one application_, is more used for fencing than any other material.

We are much in want of a valuable series of experiments on the application of various chemicals on wood to resist _burning to pieces_; without causing it to _rot speedily_.