Chapter 6

The Rigi road has several special features aside from its terrific slopes which entitle it to be considered a triumph of the engineer's skill. About midway up the mountains the builders came to a solid mass of rock, which presented a barrier that to a surface road was impassable. They determined to tunnel it, and, after an enormous expenditure of labor, finished an inclined tunnel 225 feet in length, of the same gradient as the road. A gorge in the side of the mountain where a small stream, the Schnurtobel, had cut itself a passage also hindered their way, and was crossed by a bridge of lattice girder work in three spans, each 85 feet long. The entire roadbed, from beginning to end, was cut in the solid rock. A channel was chiseled out to admit the central beam, which contains the cogs fitting the driving wheel of the locomotive. The engine is in the rear of the train, and presents the exceedingly curious feature of a boiler greatly inclined, in order that at the steeper gradients it may remain almost perpendicular. The coal and water are contained in boxes over the driving wheels, so that all the weight of the engine is really concentrated on the cogs--a precaution to prevent their slipping. The cost of the road, including three of these strangely constructed locomotives, three passenger coaches, and three open wagons, was $260,000, and it is a good paying investment. The fare demanded for the trip up the mountains is 5 francs, while half that sum is required for the downward passage, and the road is annually traversed by from 30,000 to 50,000 passengers.

Curious sensations are produced by a ride up this remarkable line. The seats of the cars are inclined like the boiler of the locomotive, and so long as the cars are on a level the seats tilt at an angle which renders it almost impossible to use them. But when the start is made the frightful tilt places the body in an upright position, and, with the engine in the rear, the train starts up the hill with an easy, gliding motion, passing up the ascent, somewhat steeper than the roof of a house, without the slightest apparent effort. But if the going up excites tremor, much more peculiar are the feelings aroused on the down grade. The trip begins with a gentle descent, and all at once the traveler looking ahead sees the road apparently come an end. On a nearer approach he is undeceived and observes before him a long decline which appears too steep even to walk down. Involuntarily he catches at the seats, expecting a great acceleration of speed. Very nervous are his feelings as the train approaches this terrible slope, but on coming to the incline the engine dips and goes on not a whit faster than before and not more rapidly on the down than on the up grade. Many people are made sick by the sensation of falling experienced on the down run. Some faint, and a few years ago one traveler, supposed to be afflicted with heart disease, died of fright when the train was going over the Schnurtobel bridge. The danger is really very slight, there not having been a serious accident since the road was opened. The attendants are watchful, the brakes are strong, but even with all these safeguards, men of the steadiest nerves cannot help wondering what would become of them in case anything went wrong.

Bold as was the project of a railroad on the Rigi, a still bolder scheme was broached ten years later, when a daring genius proposed a railroad up Mt. Vesuvius. A railroad up the side of an ordinary mountain seemed hazardous enough, but to build a line on the slope of a volcano, which in its eruption had buried cities, and every few years was subject to a violent spasm, seemed as hazardous as to trust the rails of an ordinary line to the rotten river ice in spring time. The proposal was not, however, so impracticable as it looked. While the summit of Vesuvius changes from time to time from the frequent eruptions, and varies in height and in the size of the crater, the general slope and contour of the mountain are about the same to-day as when Vesuvius, a wooded hill, with a valley and lake in the center of its quiescent crater, served as the stronghold of Spartacus and his rebel gladiators. There have been scores of eruptions since that in which Herculaneum and Pompeii were overthrown, but the sides of the mountain have never been seriously disturbed.

A road on Vesuvius gave promise of being a good speculation. Naples and the other resorts of the neighborhood annually attracted many thousands of visitors, and a considerable number of these every year ascended the volcano, even when forced to contend with all the difficulties of the way. Many, however, desiring to ascend, but being unable or unwilling to walk up, a chair service was established--a peculiar chair being slung on poles and borne by porters. In course of time the chair service proved to be inadequate for the numbers who desired to make the ascent, and the time was deemed fit for the establishment of more speedy communication.

Notwithstanding the necessity, the proposal to establish a railroad met with general derision, but the scheme was soon shown to be perfectly practicable, and a beginning was made in 1879. The road is what is known as a cable road, there being a single sleeper with three rails, one on the top which really bore the weight, and one on each side near the bottom, which supported the wheels, which coming out from the axle at a sharp angle, prevented the vehicle from being overturned. The road covers the last 4,000 feet of the ascent, and the power house is at the bottom, a steel cable running up, passing round a wheel at the top and returning to the engine in the power house. The ascent to the lower terminus of the road is made on mules or donkeys; then, in a comfortable car, the traveler is carried to a point not far from the crater. The car is a combined grip and a passenger car, similar in some points to the grip car of the present day, while the seats of the passenger portion are inclined as in the cars on the Rigi road. But the angle of the road being from thirty-three to forty-five degrees, makes both ascent and descent seem fearfully perilous. Every precaution, however, is taken to insure the safety of passengers; each car is provided with several strong and independent brakes, and thus far no accident worth recording has occurred. The road was opened in June, 1880. Although there have been several considerable eruptions since that date, none of them did any damage to the line but what was repaired in a few hours.

The fashion thus set will, no doubt, be followed in many other quarters. Wherever there is sufficient travel to pay working expenses and a profit on a steep grade mountain road it will probably be built. Already there is talk of a road on Mont Blanc, of another up the Yungfrau, and several have been projected in the Schwartz and Hartz mountains. A route on Ben Nevis, in Scotland, is already surveyed, and it is said surveys have also been made up Snowden, with a view to the establishment of a road to the summit of the highest Welsh peak. Sufficient travel is all that is necessary, and when that is guaranteed, whenever a mountain possesses sufficient interest to induce people to make its ascent in considerable numbers, means of transportation, safe and speedy, will soon be provided. The modern engineer is able, willing and ready to build a road to the top of Mt. Everest in the Himalayas if he is paid for doing so.--_St. Louis Globe-Democrat._

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To clean hair brushes, wash with weak solution of washing soda, rinse out all the soda, and expose to sun.

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THE MARCEAU.

The Marceau, the last ironclad completed and added to the French navy, was put in commission at Toulon in April last, and has lately left that town to join the French squadron of the north at Brest. The original designs of this ship were prepared by M. Huin, of the French Department of Naval Construction, but since the laying down of the keel in the year 1882 they have been very considerably modified, and many improvements have been introduced.

Both ship and engines were constructed by the celebrated French firm, the Société des Forges et Chantiers de la Mediterranée, the former at their shipyard in La Seyne and the latter at their engine works in Marseilles. The ship was five years in construction on the stocks, was launched in May, 1887, and not having been put in commission until the present year, was thus nearly nine years in construction. She is a barbette belted ship of somewhat similar design to the French ironclads Magenta, now being completed at the Toulon arsenal, and the Neptune, in construction at Brest.

The hull is constructed partly of steel and partly of iron, and has the principal dimensions as follows. Length, 330 ft. at the water line; beam, 66 ft. outside the armor; draught, 27 ft. 6 in. aft.; displacement, 10,430 English or 10,600 French tons. The engines are two in number, one driving each propeller; they are of the vertical compound type, and on the speed trials developed 11,300 indicated horse power under forced and 5,500 indicated horse power under natural draught, the former giving a speed of 16.2 knots per hour with 90 revolutions per minute. The boilers are eight in number, of the cylindrical marine type, and work at a pressure of 85.3 lb. per square inch. During the trials the steering powers of the ship were found to be excellent, but the bow wave is said, by one critic, to have been very great.

The ship is completely belted with Creusot steel armor, which varies in thickness from 9 in. forward to 17¾ in. midships. In addition to this belt the ship is protected by an armored deck of 3½ in., while the barbette gun towers are protected with 15¾ in. steel armor with a hood of 2½ in. to protect the men against machine gun fire. As a further means of insuring the life of the ship in combat and also against accidents at sea, the Marceau is divided into 102 water-tight compartments and is fitted with torpedo defense netting. There are two masts, each carrying double military tops; and a conning tower is mounted on each mast, from either of which the ship may be worked in time of action, and both of which are in telegraphic communication with the engine rooms and magazines. Provision is made for carrying 600 tons of coal, which, at a speed of 10 knots, should be sufficient to supply the boilers for a voyage of 4,000 miles.

The armament of the Marceau is good for the tonnage of the ship and consists principally of four guns of 34 centimeters (13.39 in.) of the French 1884 model, having a weight of 52 tons, a length of 28½ calibers, and being able to pierce 30 in. of iron armor at the muzzle. The projectiles weigh 924 lb., and are fired with a charge of 387 lb. of powder. The muzzle velocity has been calculated to be 1,968 ft. per second. The guns are entirely of steel and are mounted on Canet carriages in four barbette towers, one forward, one aft, and one on each side amidships. On the firing trials both the guns and all the Canet machinery, for working the guns and hoisting the ammunition, gave very great satisfaction to all present at the time. In addition to the above four heavy guns there are, in the broadside battery, sixteen guns of 14 centimeters (5.51 in.), eight on each side, and a gun of equal caliber is mounted right forward on the same deck. The armament is completed by a large number of Hotchkiss quick-firing and revolver guns and four torpedo tubes, one forward, one aft, and one on each side.

The crew of the Marceau has been fixed at 600 men, and the cost is stated to have been about $3,750,000.--_Engineering_.

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[Continued from SUPPLEMENT, No. 820, page 13097.]

A REVIEW OF MARINE ENGINEERING DURING THE PAST DECADE.[1]

[Footnote 1: Paper read before the Institution of Mechanical Engineers, July 28, 1891.]

BY MR. ALFRED BLECHYNDEN, OF BARROW-IN-FURNESS

_Steam Pipes_.--The failures of copper steam pipes on board the Elbe, Lahn, and other vessels have drawn serious attention both to the material and to the modes of construction of the pipes. The want of elastic strength in copper is an important element in the matter; and the three following remedies have been proposed, while still retaining copper as the material. First, in view of the fact that in the operation of brazing the copper may be seriously injured, to use solid drawn tubes. This appears fairly to meet the main dangers incidental to brazing; but as solid drawn pipes of over 7 inches diameter are difficult to procure, it hardly meets the case sufficiently. Secondly, to use electrically deposited tubes. At first much was promised in this direction; but up to the present time it can hardly be regarded as more than in the experimental stage. Thirdly, to use the ordinary brazed or solid drawn tubes, and to re-enforce them by serving with steel cord or steel or copper wire. This has been tried, and found to answer perfectly. For economical reasons, as well as for insuring the minimum of torsion to the material during manufacture, it is important to make as few bends as possible; but in practice much less difficulty has been experienced in serving bent pipes in a machine than would have been expected. Discarding copper, it has been proposed to substitute steel or iron. In the early days of the higher pressures, Mr. Alexander Taylor adopted wrought iron for steam pipes. One fitted in the Claremont in February, 1882, was recently removed from the vessel for experimental purposes, and was reported upon by Mr. Magnus Sandison in a paper read before the Northeast Coast Institution of Engineers and Shipbuilders.[2] The following is a summary of the facts. The pipe was 5 inches external diameter, and 0.375 inch thick. It was lap welded in the works of Messrs. A. & J. Stewart. The flanges were screwed on and brazed externally. The pipe was not lagged or protected in any manner. After eight and a half years' service the metal measured where cut 0.32 and 0.375 inch in thickness, showing that the wasting during that time had been very slight. The interior surface of the tube exhibited no signs of pitting or corrosion. It was covered by a thin crust of black oxide, the maximum thickness of which did not exceed 1/32 inch. Where the deposit was thickest it was curiously striated by the action of the steam. On the scale being removed, the original bloom on the surface of the metal was exposed. It would thus appear that the danger from corrosion of iron steam pipes is not borne out in their actual use; and hence so much of the way is cleared for a stronger and more reliable material than copper. So far the source of danger seems to be in the weld, which would be inadmissible in larger pipes; but there is no reason why these should not be lapped and riveted. There seems, however, a more promising way out of the difficulty in the Mannesmann steel tubes which are now being "spun" out of solid bars, so as to form weldless tubes.

[Footnote 2: Transactions Northeast Coast Institution of Engineers and Shipbuilders, vol. 7, 1890-91, p. 179.]

TABLE I.--TENSILE STRENGTH OF GUN METAL AT HIGH TEMPERATURES.

+------------+-------------+-------------+------------+ | | | | | Composition |Temperature | Tensile | Elastic | Elongation | of | of oil | strength | limit | in | gun metal. | bath. | per square | per square | length of | | | inch. | inch. | 2 inches | --------------+------------+-------------+-------------+------------+ Per cent. | Fahr. | Tons | Tons | Per cent. | Copper 87 /| 50° | 12.34 | 8.38 | 14.64 | Tin 8 / | | | | | Zinc 3½ \ | | | | | Lead 1½ \| 400° | 10.83 | 6.30 | 11.79 | --------------+------------+-------------+-------------+------------+ Copper 87 /| 50° | 13.86 | 8.33 | 20.30 | Tin 8 { | | | | | Zinc 5 \| 458° | 10.70 | 7.43 | 12.42 | --------------+------------+-------------+-------------+------------+

Cast steel has been freely used by the writer for bends, junction pieces, etc., of steam pipes, as well as for steam valve chests; and except for the fact that steel makers' promises of delivery are generally better than their performance, the result has thus far been satisfactory in all respects. These were adopted because there existed some doubt as to the strength of gun metal under a high temperature; and as the data respecting its strength appeared of a doubtful character, a series of careful tests were made to determine the tensile strength of gun metal when at atmospheric and higher temperatures. The test bars were all 0.75 in diameter, or 0.4417 square inch sectional area; and those tested at the higher temperatures were broken while immersed in a bath of oil at the temperature here stated, each line being the mean of four experiments. The result of these experiments was to give somewhat greater faith in gun metal as a material to be used under a higher temperature; but as steel is much stronger, it is probably the most advisable material to use, when the time necessary to procure it can be allowed.

_Feed Heating_.--With the double object of obviating strain on the boiler through the introduction of the feed water at a low temperature, and also of securing a greater economy of fuel, the principle of previously heating the feed water by auxiliary means has received considerable attention, and the ingenious method introduced by Mr. James Weir has been widely adopted. It is founded on the fact that, if the feed water as it is drawn from the hot well be raised in temperature by the heat of a portion of steam introduced into it from one of the steam receivers, the decrease of the coal necessary to generate steam from the water of the higher temperature bears a greater ratio to the coal required without feed heating than the power which would be developed in the cylinder by that portion of steam would bear to the whole power developed when passing all the steam through all the cylinders. The temperature of the feed is of course limited by the temperature of the steam in the receiver from which the supply for heating is drawn. Supposing, for example, a triple expansion engine were working under the following conditions without feed heating: Boiler pressure, 150 lb.;--indicated horse power in high pressure cylinder 398, in intermediate and low pressure cylinders together 790, total, 1,188; and temperature of hot well 100° Fahr. Then with feed heating the same engine might work as follows: The feed might be heated to 220° Fahr., and the percentage of steam from the first receiver required to heat it would be 12.2 per cent.; the indicated horse power in the high pressure cylinder would be as before 398, and in the intermediate and low pressure cylinders it would be 12.2 per cent, less than before, or 694, and the total would be 1,092, or 92 per cent. of the power developed without feed heating. Meanwhile the heat to be added to each pound of the feed water at 220° Fahr. for converting it into steam would be 1,005 units against 1,125 units with feed at 100° Fahr., equivalent to an expenditure of only 89.4 per cent. of the heat required without feed heating. Hence the expenditure of heat in relation to power would be 89.4 + 92.0 = 97.2 per cent., equivalent to a heat economy of 2.8 per cent. If the steam for heating can be taken from the low pressure receiver, the economy is about doubled. Other feed heaters, more or less upon the same principle, have been introduced. Also others which heat the feed in a series of pipes within the boiler, so that it is introduced into the water in the boiler practically at boiling temperature; this is economical, however, only in the sense that wear and tear of the boiler is saved; in principle the plan does not involve economy of fuel.

_Auxiliary Supply of Fresh Water_.--Intimately associated with the feed is the means adopted for making up the losses of fresh water due to leakage of steam from safety valves, glands, joints, etc., and of water discharged from the air pumps. A few years ago this loss was regularly made up from the sea, with the result that the water in the boilers was gradually increased in density; whence followed deposit on the internal surfaces, and consequent loss of efficiency, and danger of accident through overheating the plates. With the higher pressures now adopted, the danger arising from overheating is much more serious, and the necessity is absolute of maintaining the heating surfaces free from deposit. This can be done only by filling the boiler with fresh water in the first instance, and maintaining it in that condition. To do this two methods are adopted, either separately or in conjunction. Either a reserve supply of fresh water is carried in tanks or the supplementary feed is distilled from sea water by special apparatus provided for the purpose. In the construction of the distilling or evaporating apparatus advantage has been taken of two important physical facts, namely, that, if water be heated to a temperature higher than that corresponding with the pressure on its surface, evaporation will take place; and that the passage of heat from steam at one side of a plate to water at the other is very rapid. In practice the distillation is effected by passing steam, say from the first receiver, through a nest of tubes inside a still or evaporator, of which the steam space is connected either with the second receiver or with the condenser. The temperature of the steam inside the tubes being higher than that of the steam either in the second receiver or in the condenser, the result is that the water inside the still is evaporated, and passes with the rest of the steam into the condenser, where it is condensed, and serves to make up the loss. This plan localizes the trouble of deposit, and frees it from its dangerous character, because an evaporator cannot become overheated like a boiler, even though it be neglected until it salts up solid; and if the same precautions are taken in working the evaporator which used to be adopted with low pressure boilers when they were fed with salt water, no serious trouble should result. When the tubes do become incrusted with deposit, they can be either withdrawn or exposed, as the apparatus is generally so arranged; and they can then be cleaned.