1st substance, in which it is allowed to remain until it is thoroughly heated; it is then taken out of this second vessel, and, while hot, is coated with a resinous composition, consisting of a mixture of ground rosin or resinous matter, and mahogany or other woody dust, combined in any proportions that may be found to answer the purpose; or instead of using rosin in this mixture, Archangel pitch or any other resinous substances may be used; or instead of either of the foregoing, the blocks or lumps may be coated with a varnish composed of rosin and naphtha, or gutta-percha and naphtha, or other similarly adhesive body,-the object of this lastmentioned process being to confine any unpleasant odour, and prevent the escape of any of the volatile matters with which the wood or other substance was first impregnated; it is then finished by being covered over with mahogany veneer or other suitable dust. When shale oil or petroleum is used to render the wood inflammable, they must be subjected to distillation previously to being mixed with the wood, for the purpose of removing the spirit or lighter oil from either. Or, instead of preparing the wood in blocks, as herein before specified, it is cut into oblong strips, and at about the centre of each of these a hole is bored, and through the holes in these or any other number of such pieces, a tightly-fitting wooden pin is driven, for the purpose of keeping each of the pieces at a distance from one another; and after any number of pieces are thus put together, they are subjected to any of the before-mentioned processes for rendering them inflammable. Or, instead of holding the pieces or blocks together by means of a wooden pin or dowel, they may be first subjected to the processes for rendering them inflammable, and while hot, and being subjected to the process of coating with a resinous composition, smaller pieces of wood are placed between each of the before-mentioned blocks, and the resinous coating, on cooling, thus holds several pieces together. Or, instead of first impregnating blocks with any other inflammable substances, as hereinbefore described, they may be at once coated with the resinous composition, and several of them fastened together by the cooling of the coating, as in the last-mentioned process. In the substitution of this species of fuel for coal, coke, or other substances used for the generation of steam, or other similar purposes, the blocks may be used in much larger pieces than for the before-mentioned purposes. Or, lumps of peat may be boiled in vessels containing any of the inflammable oils already specified; and when the peat is thoroughly saturated, it is taken out, while hot, and compressed or rolled into blocks or lumps, and while still in a hot state, these blocks are coated with a composition consisting of coal dust and coal-tar pitch, in which state it is ready for use, thus producing a highly inflammable fuel. The patentee claims, "First,-the impregnating pieces or blocks of wood, coke, peat, or other similar porous or vegetable substances, with any of the foregoing inflammable oils or ingredients, as described. Second,-the system or mode of coating such saturated blocks of wood, coke, peat, or other similar porous substances, with any adhesive or resinous composition, as described. Third, the coating of blocks of wood, fastened together as described. Fourth, the application and use of saturated blocks of wood, coke, or peat, as fuel, to be used in the generation of steam, or for other purposes, as described." 1st Scientific Notices. INSTITUTION OF CIVIL ENGINEERS. February 16th, 1864. J. R. Mc CLEAN, PRESIDENT, IN THE CHAIR. The read was, paper "The actual state of the works on the Mont Cenis Tunnel, and description of the machinery employed," by Mr. THOMAS SOPWITH, junior. THIS tunnel would form the completing link of the Victor Emmanuel Railway, and be the means of putting France and Italy in direct railway communication. The railway on the French side was already opened to St. Michel, in Savoy, and on the Italian side to Susa, in Piedmont. When the whole line was completed, the mails and traffic with India might perhaps be advantageously transferred from Marseilles to some Italian port, as the Mediterranean sea transit would thus be materially shortened. During the last twenty years many routes had been surveyed and recommended for crossing the great barrier of the Alps. Of these, that by the Mont Cenis was generally considered the most feasible; and it was only a question, whether the mountain should be crossed by a series of inclines, or whether a tunnel should be made. In 1857, Messrs. Sommeiller, Grandis, and Grattoni, brought before public notice a new system of boring by machinery, instead of by hand labour. A Government commission was appointed to examine and report upon it, and to see if it could be applied to the boring of the tunnel under Mont Cenis. Their report was favourable, and M. Sommeiller and his partners were shortly afterwards charged with the execution of the work. The ends only were available for attack, it being impossible, as was known from the first, to sink shafts. It was feared that the ventilation would seriously retard, or altogether prevent, the completion of the tunnel; but this fear was uncalled for, as the artificial ventilation in collieries overcame greater natural difficulties, and the ventilating current passed through a longer distance than could possibly be required in this tunnel. M. Sommeiller also proposed to use compressed air for driving the machinery, and calculated that on its escape, a volume of fresh air would be supplied, adequate to the requirements of the workmen. The tunnel at the Modane or French side was of the following dimensions :- -25 feet 3 inches wide at the base, 26 feet 2 inches wide at the broadest part, and 24 feet 7 inches in height; the arch being nearly a semicircle. At Bardonnèche the height was increased 11 inches. The exact length between the ends was 7.5932 miles. The present ends would not be the permanent entrances, as it was intended that a curved gallery should leave the tunnel at the north side, 415 yards from the end, and at the south side, 277 yards. At Modane, the tunnel was built entirely with stone; at Bardonnèche, for the greater part, the side walls only were of stone, and the remainder of brick. The Bardonnèche end was 434 feet higher than that at Modane. For one-half the length of the tunnel, therefore, from Modane to the middle, the gradient would be 1 in 45; the other side. being driven with only sufficient fall, 1 in 2000, to allow of the water escaping. When the tunnel was complete, it was expected that there would be a constant current of air from the north to the south: the latter was not only the higher end, but the air was more rarified and exposed to the heat of the sun, whilst the entrance at Modane was under the shade of the mountain. The establishment consisted, at each end, of machinery for compressing the air, workshops for making and repairing machinery, offices, storehouses, residences for the engineers, and barracks for the workmen. At Modane, the entrance of the tunnel was 328 feet above the bottom of the valley, where the workshops were placed, with which there was a communication by means of an inclined plane, worked by a water balance. Different systems of tunnelling by machinery had been tried in England, amongst others, one by Captain Penrice, R.E., in which it was intended to drive a gallery about 4 feet diameter, and by means of repeated blows from a heavy frame loaded with knives, to reduce the whole of the excavated materials to small chippings and dust. It seemed, however, to the author, that any system of tunnelling must be deficient, which did not make so cheap and readily-applicable a power as gunpowder available; and that by the trituration of the rock to such small particles, as in Captain Penrice's system, a great amount of work was unnecessarily performed. In M. Sommeiller's system, whilst machinery was employed for accelerating the progress usually made by hand labour, gunpowder was also available. He had succeeded in producing a compact machine, not weighing more than 6 cwt., which could pierce a common borehole, about 1 inch diameter, and 3 feet deep, into a rock, in twenty minutes, where two miners would have required two hours. Further, he had arranged a moveable support, capable of carrying eleven such machines, any one of which could be worked at almost any angle, and of allowing the free action of each, in a gallery 10 feet square. This support could be removed when it was necessary to explode the holes bored by the machines. The machine was of very ingenious construction. It consisted of two parts:-one, a cylinder for propelling the borer against the rock; the second, a rotary engine for working the valve of the striking cylinder, turning the borer on its axis at each successive stroke, and advancing or retiring the striking cylinder, as occasion required. It gave 250 blows per minute. The effective pressure on the piston, in striking, was 216 lbs.; the length of the stroke was from 2 inches to 7 inches. Although simplified as much as possible, the nature of the work the machines performed was so severe, that they were liable to frequent derangement, and a large stock was kept on hand. The cost of each machine was about £80. The compressed air was used at a pressure of five atmospheres above atmospheric pressure, and was conveyed to the "fore-head" of the advanced gallery by a pipe 7 inches in diameter. The advanced gallery was the only place where the machines were used; the enlarging of the tunnel to the full size, walling, &c., were performed by manual labour. The system of working was to bore eighty holes in the forehead of the advanced gallery. The frame and machines were then withdrawn, and a set of men charged and fired the holes: afterwards replaced by another set, to remove the déblais. The division of time amongst the different classes of labour was very variable. It might, however, be averaged as Thus there were almost two complete shifts every twenty-four hours. An alignment was made about once in three months, from an observatory at each end. As yet no error had been detected. Three or four large holes, each about 4 inches diameter, were bored near the centre of the fore-head. These were not charged and exploded, their purpose being to weaken the surrounding rock. The remainder were charged; those adjoining the centre being first fired,— and the result of these explosions was a cavity. The remaining holes were then exploded from this cavity outwards. The workmen were industrious, under circumstances which required more than ordinary perseverance. A premium on their wages was given for more than a certain advancement per day. At the time of the author's visit, one metre per day was the standard. The déblais resulting from the explosion of the eighty holes was removed in small wagons. Its removal was well organised, and, considering the circumstances, quickly effected. It would be much accelerated, if it was possible to construct an iron frame strong enough to be placed close to the fore-head at the time of the explosion, and receive without injury the products of explosion, which could be removed en masse, or nearly so. Two descriptions of machines for compressing air were in use,one on the hydraulic ram principle, the other resembling a pump. In the first, the water was admitted, with a pressure of 85 feet, into a column, or vessel, containing air, about 14 feet high, and 2 feet in diameter. The water, by its momentum, rushed up the column, compressed the volume of air, and forced it through a valve into a reservoir. The pressure valve being closed, the exhaust valve was opened, and the water fell in the column; at the same time its place was taken by air, and the machine became ready for another stroke. This machine made 2 strokes per minute, and was capable of supplying about 20 cubic feet of air, compressed to five atmospheres, per minute. The other machine consisted of a horizontal pump and two vertical branches. The piston was surrounded by water, which rose and fell alternately in the two columns: when it rose, compressing the air, and forcing it through the outlet valve; and when it fell, creating a vacuum, which was filled by air at atmospheric pressure. The tunnel, on the 30th June, 1863, had been driven (including the advanced gallery) at Modane, 1092.25 metres, and at Bardonnèche 1450·00 metres, The advancement in June last, at Modane, was at the rate of 4.719 feet per day. At this rate of progress at both ends, the tunnel would be finished in 9 years 2 months from that time. It was not, however, too much to expect a progress of 2 metres per day at each end, seeing that machines had only been in use at Bardonnèche about two years and a half, and at Modane half a year. A great part of that time had been taken up in experiments, and the men were not thoroughly habituated, as yet, to the manipulation of the machines. The machines were also being much improved. With an average rate of 2 metres per day from June 30th, 1863, 6 years 7 months would be required for the completion of the tunnel, as compared with 26 years 3 months by hand labour, at 1655 feet per day at each end,-the average rate of progress previous to the introduction of the machinery. The machinery in use at Mont Cenis was made, for the greater part, at Seraing, near Liége. M. Sommeiller confidently expected an advance, ment of 3 metres per day at each end. If that were the average from June 30th, 1863, the work would be completed in 4 years 8 months from that time. In the advanced gallery at Modane, the number of workmen employed during the twenty-four hours was as follows: 344 men were also engaged in enlarging and walling, giving a total employed underground of 471, and including blacksmiths, stonedressers, and other labourers at the surface, there were employed at the tunnel ... ... Mechanics, brakesmen, &c., in the workshops, machinery, &c. Or a total at Modane of ... ... ... 700 240 At Bardonnèche the number was greater; 1200 to 1400 being generally employed,—giving a total of 2540 on the works. The result of a rough comparison was to show that, in the present development of the Sommeiller system, an advancement three times quicker than by hand labour might be effected, but at about two and a half times the cost; judging rather of places where it might be generally applied, than by the Mont Cenis only. The proportion of two and a half to one increase of cost, referred only to what was known as mining charges in the advanced gallery, i. e. wages, tools, candles, and gunpowder. This proportion was notably diminished in the case of a railway tunnel, where enlarging, timbering, walling, laying of rails, &c., were charges common to both systems. In the case of a tunnel through rock, costing, when completed, £30 per yard, the two systems might compare as follows::-an increased advancement in favour of machinery of 3 to 1, at an increased cost of 4 to 3. The ventilation was good in the advanced gallery, the exhaust air from the machines affording an ample supply. During the time of exploding the holes, a jet of air was left open. Further back, where the men were employed in enlarging the tunnel, the ventilation was insufficient. The tunnel was, therefore, being divided with a horizontal brattice, the upper section being in communication with a chimney on the mountain side. The air was intended to pass along the under VOL. XIX, 2 F |