Part 2

Until the last quarter of a century, zinc was but little used, but of late it has taken the place for many useful purposes where lead was formerly used, principally owing to its cheapness and lightness. Zinc is a hard metal of a grayish colour, not easily bent but rather brittle, but when made nearly red hot, it is capable both of being rolled out into sheets and being beaten into form by the hammer. Zinc is about six-and-three-quarter times heavier than water. Like many other metals, zinc is volatile, that is to say, when heated to a certain extent it passes off into vapour, and there is no doubt, the reason that zinc was not known or used of old was that it was chiefly lost in “smelting,” or getting it from its ores. Zinc is now obtained by a sort of distillation; the ores are mixed with the flux, &c., in a large earthen crucible or pot, from which an iron tube passes into a vessel of water, the lid is securely fastened on, and as the heat is urged the zinc is driven off in vapour, passes down the tube and condenses in the water. The zinc of commerce is obtained chiefly from the ore known by the name of “calamine stone,” which is zinc in combination with oxygen and carbonic acid. A substance called “zinc white” has been lately introduced as a substitute for white lead, and would certainly supersede it, but the zinc is found to be deficient in “body,” which means, the power of covering anything over which it is laid-on in a thin layer, but as zinc white does not blacken in foul air, and white lead does, it has a great advantage, and it is to be hoped that some improvement in its manufacture may improve its “body.” Zinc is chiefly used for roofs, gutters, water-pipes, cisterns, and various vessels for holding water, as it does not rust so easily as iron. What is called “galvanised iron,” is iron dipped into melted Zinc in the same way that tin-plate is.

MERCURY.

Mercury, or quicksilver, is known from all other metals by being fluid at the ordinary temperature of the air. This is only owing to its extreme fusibility, for at 72 degrees below the freezing point of water, it also becomes solid, and may be hammered out or cut by a knife; it is very heavy, being about fifteen-and-a-half times that of water, so that most of the metals will float on its surface; it has a bright lustre and is almost as white as silver. It is found both in the fluid metallic state, and in combination with sulphur, in which last state it is called “cinnabar;” this is a heavy mass of a deep red color, and when ground to powder, of a most magnificent red, and is the vermillion so well known as a pigment; this vermillion is, however, most frequently manufactured by combining the mercury and sulphur, both first purified, in this way a more brilliant color is produced than can be got from the cinnabar. The metal is extracted by heating the cinnabar with iron-filings or lime in a retort, by which means the mercury distils over and the sulphur is left behind united with the iron or lime.

Mercury is used for many purposes in the arts and sciences, for barometers, thermometers, compensating pendulums for clocks, &c., and also in the processes of water-gilding, looking glass silvering, and in the Daguerreotype process. The combinations of mercury with other metals are called “amalgams.”

GOLD.

Illustration: GOLD (‡ NUGGET).

Gold is the heaviest of the metals with the exception of Platinum, being rather more than nineteen times heavier than water; it is of a bright yellow color, and is not tarnished by exposure to the air or moisture, hence its usefulness in ornamenting frames, cornices, &c. Gold is chiefly used, in the form of coin, as the medium of exchange; for ornamental purposes, such as jewellery; for gilding, and for staining glass, to which it gives a beautiful ruby-red color. Gold coin contains about one twelfth part, by weight, of copper, this is added to give it hardness and consequently cause it to lose less by wear in use. Gold is not dissolved by any of the pure acids, but a mixture of hydrochloric and nitric acids will dissolve it in consequence of giving out chlorine, an element which freely dissolves gold.

Gold is capable of being beaten out into leaves of extreme thinness, and also of being drawn into wire of such thinness that five hundred feet of it weigh but one grain.

SILVER.

Illustration: SILVER.

Silver is the whitest of the metals; it is about ten-and-a-half times heavier than water; it does not easily tarnish by the air, and is not converted into dross by heat continued for any length of time, or, in chemical language, it is not oxydised; it is chiefly used for coin and for ornamental purposes where its cleanliness and beauty are strong qualities to recommend it. Many kinds of lead ore contain silver, and when this is in sufficiently large proportion to pay for its extraction, the reduced lead is subjected to the flame of a furnace which is blown on to it with a strong blast, the flame melts the lead and converts it into an oxide called “litharge,” which is in the form of reddish scales, and as these are formed the blast blows them off; in this way the lead is gradually consumed, leaving the silver with but a small quantity of lead, this is put on to a cup made of bone ashes called a “cupel,” hence this operation is called “cupellation,” the heat is then raised, and the lead which remains with the silver, forming a liquid glass with the bone ashes, sinks into them, leaving the silver bright and pure. Silver in some districts is extracted from its ores by what is called “amalgamation;” the finely powdered ore is mixed with water, some cuttings of iron and quicksilver, and turned round in a barrel for a considerable time, when the quicksilver is drawn off through a small hole, and is found to contain all the silver in the ore, together with some other metals. The quicksilver is got rid of, first by pressing and then by distillation; so that it is all recovered for a second operation. What remains is separated from the other metals, which it may have been mixed with by different processes, according to the nature of these metals.

The standard silver of the Mint is what is called 22 carats fine (nearly), that is to say, 22 parts in 24, the two parts being copper; this is done to harden it. The silvering of looking-glasses is made of a compound of tin and mercury, but a process for really silvering looking-glasses has been patented by Mr. Drayton; it consists of precipitating silver from its solution by means of the oil of Cassia, or some other volatile oil: the process is far too expensive for general use or for large plates. Silver leaf is made and used in the same way that gold leaf is.

PLATINUM.

Platinum is a metal of a white color, and is the heaviest substance known, being more than twenty-one times heavier than water. It is capable of being welded and wrought out by the hammer like iron; it is not acted on by any of the acids, but, like Gold, is dissolved by chlorine or a mixture of hydrochloric and nitric acid; it does not tarnish by exposure to air, and is extremely difficult to melt, requiring the very highest heat that can be produced; these qualities render it one of the most useful of the metals to the chemist, furnishing him with retorts, crucibles, and evaporating dishes suitable for many purposes; its high price, however, renders it not so generally used as it would otherwise be.

NICKEL.

This metal is of a white color and very difficult to melt, it is about eight times heavier than water and is chiefly obtained from the ore known as kupfer-nickel, found very plentifully in Germany; this kupfer-nickel is a native arseniuret of nickel, that is, nickel in chemical combination with arsenic. It is very difficult to separate these two metals, but an effectual and cheap process has lately been devised to do so.

Nickel is attracted by the magnet similar to iron but in an inferior degree. Till lately nickel was but little used, but it now forms the basis of those compound metals known as nickel-silver, German-silver, and British-plate, all which varieties are generally employed as an economical substitute for silver; it is also used largely as a foundation on which to deposit pure silver by the electro-plating process, for which purpose it is most admirably suited being very superior to copper in consequence of its color, as the silver always wears off unequally and exposes the ground work of metal beneath. German-silver is composed of copper, nickel, and zinc, in various proportions. Nickel always forms one of the constituents of meteoric iron, those mysterious masses called aerolites, which sometimes fall to the earth.

COAL.

Illustration: MINERALS (‡ INDUSTRIAL SCENE).

This, the richest product of the mine, the well-known fuel used in almost every branch of industry as well as for warming our houses, is got from the depths of the earth, where it exists in certain localities forming what are called “coal fields” or “basins.” It is the result of changes produced during many ages upon vegetable matter buried during the various convulsions which the earth has undergone, and pressed into layers or strata of various thicknesses. To raise this valuable fuel, powerful machinery is used and deep shafts are sunk at an enormous expense.

Coal exists in various forms: the following are the most easily recognised:--

1.--Cubical coal; shining and easily broken into squarish fragments. It burns brightly.

2.--Slate coal; dull in color, splits like slate. Burns well.

3.--Cannel coal; dull color, breaks like resin, and somewhat resembles jet. Burns brilliantly, and splits with a crackling noise when in the fire. It affords the best gas.

4.--Glance, or Kilkenny coal; steel-grey color and metallic lustre. Burns without flame or smoke, somewhat like charcoal.

5.--Lignite, or brown coal; is an imperfectly formed coal.

The quantity of coal used is rapidly increasing owing to the extensive number of steam engines used, especially for navigation and railway transit; and it is a problem, not yet determined, how long the coal existing in Great Britain is likely to last; the lowest statements make it but little below a thousand years.

SULPHUR.

Sulphur, also called Brimstone, is a natural production, and is found either pure, or combined with metals forming ores, for the most part called “pyrites,” as, iron pyrites, copper pyrites, &c. In chemical language these compounds are called “sulphurets” or “sulphides.” Sulphur is one of the elements; that is to say, it is a simple body, or one neither capable of being made nor separated into other ingredients. It is crystalline, of a bright yellow color, very inflammable and volatile, burns with a blue flame and gives off pungent fumes of sulphurous acid. It is got pure by distillation from various substances containing it, and in Sicily is found nearly pure as a volcanic product. Sulphur is chiefly used for the manufacture of sulphuric acid and gunpowder, and was also largely used for making matches, but phosphorus (a still more inflammable substance) has almost superseded it in the manufacture of this necessary article.

PLASTER OF PARIS, OR GYPSUM.

Plaster of Paris is sulphate of lime--a combination of lime and sulphuric acid; and exists abundantly in various degrees of purity; it occurs plentifully in the locality of Paris, and is brought here in masses of a greenish, pink, or brown color. To prepare the gypsum it is first made red hot, to separate the water which it contains, and then ground to powder of various degrees of fineness. Plaster of Paris has the peculiar property of uniting with a certain quantity of water and forming a solid compound with it; upon this property all its usefulness depends. If a portion of Plaster of Paris be mixed with sufficient water to form a liquid of the consistence of cream, in a few minutes it will harden and become quite set, and as it dries, it will harden still more, till it is of a hardness almost equal to stone: this useful property causes it to be much used for casting figures and ornaments; cheap plaster figures, &c., are generally cast hollow, to save the plaster; this is done by pouring into the mould a certain quantity of the plaster mixed with water, and quickly turning the mould about so that it shall adhere and form a layer on all the inside of the mould; when set hard, the mould is taken to pieces and the figure finished by scraping off the marks where the mould was joined. Plaster of Paris, combined with whiting, forms what is called by plasterers “putty,” and is much used for ceilings, and similar purposes.

SALT.

Salt is one of the most widely spread and plentiful minerals which the earth gives for the use of man; all the water of the ocean derives its saline taste from salt; many springs are completely saturated and are hence called “brine springs,” and it also exists crystallized in beds within the earth of immense thickness and extending for miles each way. The salt mines of Cheshire are the finest and most extensive in England, and in some places the stratum or layer of salt is more than one hundred feet thick, perfectly white and crystallized. Salt is not a simple body, but is composed of two simple bodies or elements, chlorine and sodium, hence it is called by chemists the chloride of sodium, it can be formed by putting carbonate of soda into hydro-chloric acid (sometimes called muriatic acid,) until no more effervescence takes place, the result will taste salt and yield pure salt on evaporation. The waters of the sea are in some places evaporated by the heat of the sun in shallow hollows dug out in the beach, this is called “bay salt” and is very impure; but the chief part of the salt of commerce is procured by evaporating the waters of brine springs; this water is pumped up into large iron cisterns placed beneath slight sheds to keep the rain off, and having flues running beneath them, the first impurities are thrown away, and as evaporation goes on, the salt crystallizes and falls to the bottom of the cistern in a fine white powder; this is taken out with wooden shovels and placed in conical vessels with a hole in their lower part to drain off all the moisture; it is then dried by stoves and is fit for use; when no more salt falls down, the impure liquor, called “bittern,” is drawn off and used to procure Epsom salts from, by mixing it with sulphuric acid. The bittern contains chloride of magnesium, and the sulphuric acid changes it into sulphate of magnesia, which, when purified, forms the Epsom salts sold by druggists.

About half a million tons of salt are made in England every year. Salt, besides its general use as a condiment, and in preserving food for storing ships, &c., is also used for several manufacturing purposes. By adding sulphuric acid and heating it, the acid called “hydrochloric” is given off, which is largely used for many purposes; but the chief use made of salt by the manufacturing chemist is to prepare soda for cleansing and soap making.

STONE.

Illustration: STONE QUARRY.

Stone for building is chiefly of four kinds:--lime-stone, sand-stone, granite, and marble. Slate is never used for building, but is very suitable for roofing. The most common stone is limestone, and that brought from Portland Island is especially good for building-stone; it is called Portland stone, and it is of this stone that St. Paul’s Cathedral is built, and most of the other public buildings of London: it is rather soft when first dug from the quarry, but hardens with age. Sandstone is a very coarse kind of stone, and is only used where not much exposed to the weather; it consists of grains of sand adhering so firmly together as to form a stone of considerable hardness. Granite is a very hard stone, and very durable; so hard that it cannot well be carved, and is therefore only used where durability and plain solidity are required; London Bridge and the Euston Square Terminus of the Birmingham Railway are built of granite. Marble is a very fine heavy kind of limestone, sometimes quite white, and generally partly transparent; the white kind is very expensive, and is used for statuary, that is to say, for carving into figures, vases, &c.; it is very durable, but is too expensive for general use. Chimney-pieces, slabs for washing-stands, and other articles of that description, are also made of it.

Limestone, marble, and also chalk (a soft kind of limestone), all become changed into lime if made red hot, hence the name, limestone, is often applied to all three.

Stone quarries are those places where stone exists of a quality suitable for building purposes, and in a situation admitting of its easy removal. All stone, with the exception of granite and marble, exists in layers or strata as they are called, so that the stone can be easily split in the direction of these strata or seams. When a large piece of stone has to be removed, wedges are driven in a row into these seams, and when the stone has started, it is notched at the sides and back, so that in general a square piece is thus removed; if it be not so, it is generally made into a somewhat square before leaving the quarry, hence the name, derived from the French “_quarre_.” Granite having none of the lines of cleavage, as they are called, is broken by a row of wedges driven till a crack forms from one to the other. Slate is a clay-stone found in layers like limestone, but much more perfect; so much so, indeed, that it can be split into slices a quarter of an inch thick and one or two feet square; these, when sorted into sizes, form the slates for roofing houses. It has been much used of late in thick slabs, cut by circular saws, for making cisterns, a purpose for which it is well adapted.

WOOD.

Illustration: (‡ LOGGERS.)

Wood is an article of universal application; its lightness, strength, and the facility with which it can be worked, render it almost invaluable; although in ship-building and many of its applications to house-building iron has to some extent superseded it, yet there are so many other ways in which it is indispensable, that it may be looked upon as one of the greatest boons to mankind. There is scarcely a use to which wood may not be applied, whether as fuel for fires, timber for building, furniture both useful and ornamental, various parts of machinery, vessels to contain wine and other fluids, handles to instruments, (for in cold climates and cold weather metal cannot be handled with impunity), and indeed for all uses in which lightness, dryness, warmth, and variety of form are desirable, wood serves as an excellent material. The kind of trees that produce wood fit for building and other useful purposes are those called by the botanists _exogenous_. Amongst which the pine tribe, oak, ash, elm, and beech, stand pre-eminent; while mahogany, walnut, and rosewood are chiefly used for ornamental purposes; box-tree wood is also very useful on account of its closeness and evenness of grain; it is the wood used by engravers.

Wood when first cut is wet and heavy, but, by being exposed to the air, it shrinks and the sap dries up in it, it is therefore liable to swell and become damp in moist situations this is detrimental to its usefulness; most woods therefore are improved by being soaked a long time in water, this cleanses it from saline and extractive matters which keeps the wood damp, but which, when separated, allow the wood to shrink and harden permanently, this process is called seasoning, the same effect may be produced by exposure to the air and rain, it is generally resorted to when the timber is cut up into smaller pieces. The structure of wood is porous, hence its lightness, it has also a grain which runs the whole length of the wood in circles round its centre to the surface, one of these circles is produced every year while the tree is growing; wood is therefore capable of being cleft in the direction of the grain by a wedge, in this way builder’s laths are made. Wood cannot be cleft across the grain, but must be cut by sawing or otherwise. The pine or fir tribe produce the largest and straightest timber, but it is not so strong nor so durable as oak and many other woods.

Some specimens of the _Araucaria Excelsa_ or Norfolk Island pine, have stems upwards of three hundred feet high, and in the Crystal Palace is the bark of another gigantic tree the _Wellingtonia Gigantea_.

COTTON.

Illustration: COTTON (‡ PLANT).

Cotton consists of the fine long hairs which grow from the seeds of several varieties of _Gossypium_, a plant belonging to the natural order of _Malvaceæ_. These hairs are so long and numerous that they completely fill the pod or seed vessel; they are very delicate, and of the same size throughout, and but seldom jointed, they are each separate from the other.

The cotton plant is chiefly cultivated in America and India. In India, and some of the islands in the Indian Ocean, cotton has been cultivated, spun, and woven into textures from time immemorial. Cotton fabrics were in use in Mexico before its conquest by the Spaniards, and have been used in China for many hundred years; its chief source now is America, where more than two hundred times the quantity is grown at present than was grown there half-a-century ago; but the internal communication brought about by railways in India, may, in all probability, revive the cultivation of cotton in that country; the cost of conveyance from the interior having been one of the greatest drawbacks to its exportation.

Cotton is not only cheaper than linen (which is woven from flax), but has several advantages over it: it takes dyes much better, and produces brighter colors; the improvements made in the machinery for spinning and weaving cotton, have not only enabled us to match the spinners and weavers of India, which, for a long time supplied nearly the whole of Europe, but at the present time, cotton cloths of English manufacture are exported to India for the purpose of clothing the natives of that country.

FLAX.

Illustration: FLAX (‡ PLANT).

Flax is obtained from the stalks of the flax plant _Linum Usitatissimum_, it is supposed to have been originally brought from Egypt, where linens have been woven from its fibres from time immemorial. It is now found growing wild in this country, and is cultivated in most parts of Europe, either for its stalks to make flax, or for its seed (linseed), which is used for fattening cattle, and yields an oil (linseed oil) much used in the making of paint. The plant grows to two or three feet in height, bears a blue flower in July, and has a great hollow stem; when gathered, it is pulled up by the roots. The fibres of flax are very long and even; it is the inner part which yields the best fibres.

SILK.

Illustration: SILK (‡ WORMS).