passengers. The single posts afford abundant lateral stability, as they are subjected to but very little lateral strain. But considerable difficulty was found in giving them sufficient stability to meet the longitudinal strain occasioned by the momentum of the train when the brakes are applied, there being a space left between the ends of the girders to allow for the expansion and contraction caused by changes of temperature, which prevented the longitudinal strain from being transmitted to more than two or three columns. The difficulty was met by bolting the longitudinal guard-timbers through the cross-ties to the top chord of the girders, and thus making the road longitudinally rigid by distributing the strain over the whole row of posts. One of the problems connected with building the road arose from the difficulty, in carrying it around the corners in small streets, of making the necessary curve of 90 degrees. To make the curve at a corner where the breadth of one street was 30 and that of the other 40 feet, a long girder was carried across diagonally from corner to corner, and a cross-girder carried to meet this perpendicularly from the inside corner.

As

the corner is approached the tracks are carried out on each street almost to the edge of the framework, so as to get a wide sweep at the

corner.

A design for a cheap and readily constructed pioneer or military railway for temporary purposes was experimented upon in England lately. It was planned by J. L. Haddan. It was built entirely of timber on posts, and had a central rail 7 feet from the ground, upon which the engine and carriages were balanced like panniers, and two guide-rails, one on each side, upon which the wheels worked, which were horizontal, gripping the side-rails. Such a structure was hastily put up at Whitehall by a few soldiers upon very uneven ground, the posts driven into the ground, the crosstimbers fixed and bolted, and wedges driven in to make up for any slack in the trusses, all in a short time and with ease.

The new Eddystone lighthouse will require, it is expected, five years in building. The site chosen by the engineer, Douglas, is the south reef, which will make the work of building the lower part of the structure much more difficult than in the case of the old tower, as it lies in

some places as much as 4 feet below the lowwater mark of the spring tide, and is nowhere uncovered before half tide; it is also a position much exposed to storms. The new tower will be much larger than Smeaton's, but of the same general form. The base, however, will be made perfectly cylindrical, 44 feet in diameter and 22 feet high. The lighthouse proper, resting on this substructure, will be 35 feet in diameter at the bottom, leaving a ledge around it nearly 5 feet wide, which will be used as a landing platform. To the height of 134 feet above the rock the tower will taper till its diameter is 183 feet, and above that it will curve outward again, until it is 23 feet in diameter at the top, 8 feet higher, or 142 feet above the rocky base. It will be built of granite, dovetailed and cemented together, like the old tower. The old lighthouse is 34 feet in diameter at the base and 15 feet at the top, the gallery being 61 feet above high water, and the light 68 feet. The new light will be 55 feet higher than the old one. The estimated cost is £70,000. The amount of granite used will be 69,500 cubic feet. The weight of the structure will be 5,200 tons, or nearly 3 tons of insistant load to every square foot of foundation. The walls of the hollow portion of the shaft will be 8 feet thick at the bottom, and 21 feet at the top.

The breakwater built at the mouth of the river Tees, in England, for the conservation of the river, extends from the point at the southern side of the estuary for 2 miles in a northwesterly direction, in a line which is almost straight. The work was commenced about fifteen years ago. About three fifths of the length was successfully built with furnace slag, which was simply tipped, forming a great embankment. Beyond that distance the sandy tongue which afforded a foundation for the embankment came to an end, and the slag, which was mounded up in the outer waters, was broken into small fragments and washed up by the action of the winter storms each year. The plan was accordingly adopted three years ago, on the advice of John Fowler, of Stockton-onTees, of constructing an outside wall of concrete backed up by a heavy bank of slag. The concrete wall is 19 feet broad at its base and 10 feet at the top. A staging built over it sustains a tramway of the endless-wire system, on which the concrete is brought out in tubs, while the piles which support the railway are boarded in by stout planks and the interstices calked with oakum, so as to make a series of water-tight compartments, which are filled in with the concrete. At the bottom Roman cement is employed, owing to the impossibility of excluding the water long enough for Portland cement, of which the main bulk of the wall is composed, to set. The breakwater will be completed, it is expected, in the spring of 1880. Its head is to be made circular in form, with a diameter of 100 yards. The foundation of this part will be laid by sinking barges filled

with slag and large blocks of concrete formed on shore and floated out on pontoons. On this foundation the head is to be built of concrete, and will support a lighthouse. A similar breakwater will be carried out from the opposite shore. It will extend in an easterly direction about one mile, and will terminate like the other in a circular head and lighthouse.

The dock at Bristol, in the mouth of the Avon, completed in 1877, after nine years of labor, is 1,400 feet in length and 500 feet in width, affording a water area of about 16 acres and a length of quay of 3,200 feet. The entrance to the lock from the river Avon is 350 yards long and 70 yards in average width, with a depth at spring tides of 40 feet. The large quantity of mud washed up by the tides necessitated the throwing up of a protective embankment during the construction. The wall of the dock is 40 feet high, and the foundations below the dock floor 24 to 19 feet in thickness. The footings are of lime concrete, the rest of the wall of rubble masonry faced with dressed stone. Over 1,750,000 cubic yards of material was excavated from the basin and entrance, at a cost of 18. 6d. per cubic yard.

The Huelva pier recently constructed, which forms the terminus of the Rio Tinto Railway, where the ore mined in the Rio Tinto cupriferous iron pyrites mines is transshipped, was built on a rising grade to enable the cars to be pushed up by locomotives to a height where the ore could be dumped into the holds of the vessels. The length of the pier and approach is 2,444 feet, of which 1,900 feet is on cast-iron screw-piles, driven in groups 15 feet apart, each of the 30 groups containing 8 piles and columns; the rest is made up of 29 spans of 50 feet each. Independent of the piles was a shipping-deck wharf of creosoted wood, Memel fenders, and piles.

The new harbor at Madras, which is being constructed according to designs by W. Parkes, will be the first practicable haven for large craft on the whole eastern coast of India. The harbor will be formed by a couple of breakwaters carried out to sea and then bending in toward each other, leaving an entrance between their heads 150 feet in width. The area inclosed by them is about 140 acres; the depth of water is generally 4 to 7 fathoms. The piers are to be made of blocks of concrete, weighing 27 tons each, placed on their foundation of rubble by the aid of a Titan crane. The work was commenced in the summer of 1875. In the first year the southwest monsoon washed up the marl surf-bank. The shifting of the sand up and down the coast, caused by the monsoons, was thought to be a fatal obstacle to a harbor, but it has been found that this difficulty was exaggerated. An unexpected movement of sand buried the works on the north pier in the spring of 1877. By the middle of 1878 the pier had been carried out to the distance of 700 feet, and there was no sign of further obstacles from the action of the

traveling sands. The south pier had been completed by the end of March for 425 feet, and 3 fathoms depth of water reached. The concrete, used in heavy molded blocks in the walls, is composed partly of crushed shingle and bowlders, and partly of crushed granite, mixed in due proportions with sand and cement, and hardened in boxes into blocks of 14 by 6 by 4 feet for the lower courses, weighing each 22 tons, and 27-ton blocks for the three upper courses. The molds are two thirds filled with lumps of stone before the mixture is poured in.

The great Sutro Tunnel made its first connection with the series of mines which it is to benefit within the past year. The idea of a tunnel was first conceived of by Sutro in 1860, on his first visit to the Comstock lode. Convinced by an examination of the developments that the Comstock was a true fissure-vein, he advised the opening of a deep adit from the foot-hills on the Carson River to the ore-body; but his project was then considered chimerical. Afterward engaging in a milling and amalgamating establishment at Dayton, his mind was diverted from the tunnel project, until by the destruction of his works by fire he was left without occupation and almost without means. From this time he gave up his mind to the realization of his great scheme. On the 4th of February, 1865, the Legislature of Nevada passed an act giving him a franchise of the same order as those given for the building of a toll-road, leaving the amount of toll to be settled upon between Sutro and the mining companies. After long negotiations nearly all the companies agreed on a uniform toll of $2 per ton of paying ore, to be paid after the tunnel had reached and benefited each several mine. This act was ratified by the Sutro Tunnel Act passed by the United States Congress on the 25th of July, 1866, which gave him the right of way over the public domain, the right to purchase land at the mouth of the tunnel, the ownership of all new mines which should be discovered for a distance of 2,000 feet on each side of the tunnel, and a lien on the lands of the mining companies for the payment of the toll agreed upon. After securing such vested rights, Mr. Sutro proceeded to New York, where his project was favorably entertained by capitalists; and he also visited Europe to enlist European capital in the design, but with less success. Capitalists on the Pacific coast showed themselves resolutely opposed to the scheme, and it is to the machinations of a combination of them, instigated by the Bank of California, that Sutro attributes many of the difficulties which he encountered in forming his company, and particularly the numerous bills which were presented before Congress whose covert import would deprive him of the rights already granted by Congress, to combat which required his frequent presence in Washington. The originator and energetic prosecutor of

this great mining enterprise, Adolph Heinrich Joseph Sutro, was born at Aix-la-Chapelle, Prussia, in 1830, and received a superior industrial education, his father having been a manufacturer, and he himself having been intrusted with the starting of a woolen mill at the age of nineteen. In 1850 he emigrated to California and engaged in mercantile pursuits, also interesting himself in gold-mining. After visiting the Comstock lode, as stated above, he gave his attention to the treatment of its ores, and established a mill to carry out a process studied out by him and a German metallurgist named Rahmdohr, which employment he followed until he actively engaged in promoting the scheme of the tunnel.

The work on the tunnel was first commenced on the 19th of October, 1869; but before the 1st of January, 1870, not over 460 feet had been tunneled. In the following year 1,290 feet was made. In 1871 the works were visited by a Congressional commission, composed of Generals H. G. Wright and J. G. Foster and Professor W. Newcomb; they reported that the tunnel was feasible, and could be completed in three or four years, at a cost of $4,500,000; that the Comstock was a true fissure-vein, extending down indefinitely; and that there was an unlimited quantity of lowgrade ore in the lode which could not be worked on account of the expense. In the fall of 1871, better financial arrangements having been made, a larger force of men was employed, and machinery was procured. Four vertical shafts were located, the first of which, 4,915 feet from the mouth of the tunnel, and 522 feet deep, was commenced in January, 1872, and sunk to the level of the tunnel by July in the following year. Water was troublesome in this shaft, and much pumping was necessary, two of Allison & Bannan's doubleacting cataract pumps being employed, which were very effective, raising the water 300 feet from station to station, and discharging 3,000,000 gallons per month. The second shaft, commenced at the same time with the other, is located 9,065 feet from the tunnel's mouth, and has a depth of 1,041 feet; pumping was necessary after the depth of 600 feet was attained. The level of the tunnel was reached in April, 1874. From the bottom of the first of these shafts a bore was made east and west until it met the tunnel-header. A bore was commenced from the bottom of the second shaft, but it had not been pushed over 170 feet in each direction before a large and unexpected volume of water was tapped in the west drift, which poured in so suddenly that the miners fled for their lives. In a few weeks the water had filled the shaft to its very top. The other two shafts, one situated 13,545 feet and the other 17,695 feet from the mouth, had likewise to be abandoned, when the first had been sunk to the depth of 456 feet and the other of 674 feet, on account of the unmanageable inflow of water. Another shaft, for

air only, 2,250 feet from the entrance and 211 feet in depth, was begun in May, 1872, and finished in a few weeks. In the beginning of 1871 the bore had been completed for 1,750 feet; in that year 915 feet additional was penetrated, making 2,665 feet in all; in 1872, 815 feet was made, giving a total length at the end of the year of 3,480. In 1873 there was 1,919 feet bored, including the bore which was made in each direction from the bottom of the first shaft, which amounted to 655 feat; the total length at the end of this year was 5,399 feet. In the course of 1874 six Burleigh drills were put in action, the boring before having been entirely by hand. These were provided with compressed air by a pow་ erful steam compressor of the make of the Société John Cockrill in Belgium, which was placed at Shaft No. 1. The progress made in 1874 with these aids was 2,680 feet, an average of 223 feet per month, carrying the header 8,079 feet from the entrance. In 1875 the bore penetrated 3,728 feet farther, or 11,807 feet from the mouth; the average progress per month was 310 feet. When daring this year the great body of water, which filled the second shaft and the drifts at its bottom, was encountered, the delicate and dangerous task was undertaken of tapping it with a drill-hole and allowing the water to discharge itself through the tunnel. The column of water in the shaft was over a thousand feet high; and when a hole was made 100 feet through the rock with a diamond drill, it burst forth with terrific force, but was closed up again with fragments of rock and timber which were forced into it. Bored a second time, the water forced the drill like a shot into the tunnel. In a week's time the vast volume of water had discharged itself. Another compressor, built by the Humboldt Company of Kalk, on the Rhine, was put into operation at Shaft No. 2. In the year 1876 the progress made was 3,670 feet, or 305 feet per month; the total length of the tunnel at its close was 15,477 feet. In 1877 the progress was 3,130 feet, or 260 per month, the length of the tunnel being extended to 18,607 feet. Less headway was made this latter year on account of the troublesome and dangerous nature of the rock encountered, a soft, slippery clay, which often swelled after exposure to the air to such an extent as to displace the railroad track and sometimes to break the timbering. Here the tunnel was timbered up to the face of the drift, and often lagging driven in ahead of the drift. Only light charges of gunpowder, and sometimes none at all, could be used, for fear of displacing the timbers. In 1878 the average progress was still smaller, being, up to September, only 235 feet. The same soft, treacherous rock continued, and the heat and bad air became more and more opThe total pressive as the bore advanced. length of the tunnel up to the 1st of September, 1878, was 20,489 feet. The tunnel pene

VOL. XVIII.-19 A

trated to the Savage mine, forming the first connection with the Comstock lode, on July 8th. The junction with the Savage mine was at the 1,650-foot level, at a point distant 20,018 feet from the mouth of the tunnel. A strong current of air immediately started up the shaft of the mine, and a draught entered the mouth of the tunnel. The air in the header and in the lower drifts of the mine, which was extremely noxious, was purified in a few days by the circulation, and the heat at the 2,000-foot level of the Savage mine was reduced from 120° to 90° Fahr.

The drainage of the Sutro Tunnel will be effected by a covered drain extended through its whole length and issuing at the mouth. It is necessary to cover the drain to protect life from the hot vapors of the waters, which in some of the mines stand at a temperature

of 150° to 160° Fahr. The drain is to be

built in sections simultaneously, and made of a strong and lasting character.

A branch is being built extending from a point 19,716 feet from the mouth to the Julia mine. The length of this bore is 1,400 feet. It is of the same dimensions as the main tunnel-8 feet in height by 10 in width. This branch was commenced September 1, 1878, and is expected to be completed by February 1st. It will then be extended southward beyond the Julia to Gold Hill and Gold Cañon, while

near the Belcher mine another branch will fork off toward American Flat.

A still more important extension of the tunnel will be its continuation into Mount Davidson. The point at which it enters the mountain, under Virginia City, is nearly 2,000 feet below the streets of the town. At a distance of 3,000 feet farther into the mountain the perpendicular distance from the summit to the level of the tunnel will be 3,600 feet. It is thought that rich veins of gold may be encountered in the syenite of which the mountain is composed.

The average temperature of the air at the header during the progress of the main tunnel was, in the year 1875, 821°, of the water 813°; in 1876 the average temperature in the air was 85°, in the water 86°; in 1877 the thermometer averaged 92° in the air, 93° in the water; in 1878, in the air 95°, and in the water 105°. In 1878, up to September 1st, the average flow of water per day was about 1,285,000 gallons.

A report made to the shareholders of the St. Gothard Railway in June, 1878, states that the length of bore pierced on the north side of the mountain was 3,316 metres, of which 1,018 metres was completed. On the south side 1,317 metres had been pierced. The progress has been considerably slower than was expected, on account of the hardness of the rock. The directors hope that the bore will be completed by the close of the year 1881. The estimated cost of the line of 801,000 francs per kilometre, it is hoped, may be re

duced to 622,000 francs. Three or four thousand men are kept busy most of the time on the works, and seventy of the Ferroux piercing-machines are constantly at work. The eight years' limit of time within which the work must be completed will be up on October 1, 1880, beyond which term the contractor is bound to pay $1,000 per day for six months, $2,000 per day for the next six months, and at the end of the year, if it is not yet finished, to lose every claim as well as his bond of $1,600,000. The contractor, M. Favre, has therefore sufficient motive to carry it through within the prescribed time, and sufficient energy to do it if it is possible. He is further encouraged by a bonus of $1,000 to be paid for each day prior to October 1, 1880, after the tunnel is complete. The length of the main tunnel is 48,554 feet or 9.19 miles. The difficulties of the work have been vastly greater than was expected, owing chiefly to the hardness of the rock. The miscalculations of the engineers caused a discrepancy of about $20,000,000 between the original estimate and the actual cost, which will be about $55,000,000. The deficit was so great that there was doubt whether it could be raised, until the German, Swiss, and Italian Governments restored confidence by granting considerable subsidies. The power by which the drills are worked is compressed air alone, which is compressed outside and stored up in large reservoirs. The excavated rock is drawn out of the tunnel by locomotives worked also by compressed air, as the use of steam would be impossible. The workmen suffer greatly from the foul air, which is augmented by the explosion of dynamite in the blasts, which is incessant. The exhaust air from the drills alleviates their situation by driving the foul gases toward the mouth of the tunnel. The laborers employed are of Italian nationality, and for the moderate wages of 60 cents to $1.25 a day they display great industry and endurance in their dangerous and exhausting task. Of the three lines which were projected for the St. Gothard Tunnel, the present one was chosen on account of its being the lowest above the level of the sea, thus affording less danger of snow blockades. The highest point in the open line is 3,690 feet above the level of the sea, and the highest point in the tunnel 3,785 feet. The original estimate of the time required for its completion was fifteen or sixteen years; but Louis Favre, who was the lowest bidder at $196.40 per foot of tunnel complete, agreed to deliver the works in eight years, expecting to make more profit from the premium offered for advanced completion than from the work itself. The tunnel enters the mountain on the north, near the village of Goeschenen in the canton of Uri. The elevation at this entrance is 3,637 feet. The southern entrance is near the village of Airolo in the canton of Tessin; its height above sea level is 3,756 feet. The tunnel will be the longest in the world, being 9.19 miles

in length, while the Mont Cenis Tunnel is 40,084 feet or 7.6 miles, the Hoosac Tunnel 25,040 feet or 4.74 miles, and the Sutro 20,370 feet or 3.84 miles in length. The strata of rock pierced have been for the most part gneiss and mica slate, with considerable granitic gneiss and quartz also. The gradient is rising from the northern entrance, 5.82 feet in 1,000 or 30-7 feet per mile, for the distance of 24,459 feet, where the height is 3,785 feet above the sea; the line is there level for 590 feet, and then descends 1 foot in 1,000 feet, which grade was afterward altered to 2.5 in 1,000 or 13.2 feet per mile. The tunnel is made for a double roadway, and is to be arched from one end to the other.

The plan of tunneling adopted by M. Favre was that usual in France and Belgium of laying the advance drift in the top of the cutting instead of at the bottom, as is the common practice in Germany, Switzerland, and Italy. The advance drift is 8.9 feet square. This was followed by two cuts, the side and the sole cuts. The first, in two segments, one on each side of the axis, followed about 600 feet in the rear of the advance drift, which gave space to the whole width of the arch, and then by a cut on the east wall 12 to 15 feet below the floor of the header, which was worked in two sections, one above and one below; it was 9.8 feet in width. The arches were built as soon as the side-cuts were completed, when the nature of the rock seemed to require it, the arch being supported by timbers on one side and by the ramp on the other until the ramp was excavated and the sustaining walls built in. The header is worked with machine-drills, the car carrying six, with eighteen more at hand. The number of holes bored per lineal metre has been from 13 to 20; the holes are 1 to 1.2 metre deep, or 3.28 to 3.94 feet, and 1.5 inch in diameter. In the granitic gneiss 23 holes in a metre were required, and in mica slate only 14 holes. The McKean, the Winchester, and the Burleigh drills have been used. After the holes are drilled and the car removed 90 or 120 feet away, the holes are filled with 7 to 12 cartridges each, the cartridge weighing 31 ounces and containing giant powder. For 1 cubic yard of granitic gneiss 8.82 pounds of giant powder was used, but for a yard of mica slate 46 pounds. Blasting by electricity was tried, but not found preferable. The upper holes are blasted first, and the under ones last. Little or no tamping has been used. In the side-cuts hand-drilling was employed at first, but afterward machines; the cars here are for four drills only. The side-cut averages 77 square feet. The upper section of the sole cut is about 54 square feet, and the lower one 65 square feet. In these a strong car carrying six drills is used. The rest of the tunnel, consisting of the arch section of 40.9 to 45-21 square feet, the abutment section of 58.13 square feet, and the ramp of 207-74, is excavated by hand.