the extent to which the world's commerce has developed, and the conditions under which it is carried on. It needed only the assurance that engineering art is competent to construct a channel through which the tides can wash, and monster steamships float from one sea to another, to give rise to numerous projects of this kind, the advantages of which can be calculated with tolerable precision. The piercing of the Isthmus of Suez, the most necessary to be removed of these barriers, though not the most formidable one, furnished the needed example. Even in the far East a project for a ship-canal is taking shape. It is proposed to dig a canal through the Isthmus of Krah, the narrowest part of the Malayan Peninsula. Such a cutting would shorten the commercial route to China and Japan by more than six hundred miles. The isthmus is about fifty miles wide; but the route of the proposed canal is shortened by natural water-ways on both sides. By utilizing the bed of the Pakchan River on the western coast, and that of the Iltassay on the eastern, the length of the cutting which would have to be made would probably not exceed thirty miles. The engineering difficulties are not great, as far as known. The neighboring region is fertile, and contains minerals of value, tin-mines being already established, and gold having been found in promising quantities.

The Arlberg Tunnel was a project of six or eight years' standing, and all the engineers of Austria had been called into counsel as to the best route, when a definite line was decided upon by the Government in 1880, and the work was finally begun. The only outlet for Austrian products has been either over the German lines or Italian lines of railway, so that in view of possible complications, and as a condition of political independence, it was necessary to construct this railway, at whatever cost. The success of the Mont Cenis and St. Gothard Tunnels has encouraged the Austrians to seek an independent outlet by boring through the mass of lofty mountains between Austria and Switzerland. The tunnel will be over six miles in length. It will be completed in about six years. The total cost of the railroad will be about $18,000,000.

On the American Continent the Panama Shipcanal, which has been vigorously begun, overshadows all other engineering projects now under way. The scarcely less ambitious and more striking design of a ship-railway across the Isthmus of Tehuantepec has not yet been definitely undertaken; but the scheme is more seriously considered, and appears to have a better prospect of accomplishment, than at the time of its first promulgation. The Florida Ship-canal, the Chesapeake and Delaware Shipcanal, and the Cape Cod Ship-canal are the first projects for deep-draught canals which have a prospect of being constructed in the United States. Another ship-railway scheme has been broached as a substitute for the old project for joining the Bay of Fundy and Baie Verte

on the Gulf of St. Lawrence. A railway for conveying vessels eighteen miles across the Isthmus of Chignecto would save the long and dangerous voyage between ports of the United States and ports on the St. Lawrence Gulf and River, which must now be made around Nova Scotia. The Dominion Government has this plan under consideration.

Although in the United States no new canals of importance have been opened for many years, and the impression prevails that inland water communications are destined to be superseded by railroads, in several of the Continental countries of Europe the canal systems are being extended greatly at the present time. In Great Britain no new water-ways are under construction, and the existing ones are owned by the railroad companies, and made entirely tributary to the business of the railroads, even to the extent sometimes of abandoning their operation. Of 4,200 miles of inland navigation in Great Britain, fully 40 per cent have been purchased, leased, or subsidized by the railway companies. The most active country in the extension of water communications is Germany. The Government's plan for uniting by a system of canals the Elbe, the Weser, the Ems, the Rhine, and the Meuse, is maturing. The system, connecting with the canal systems of Belgium, France, and Holland, it is expected will be further expanded and joined to the canals of East Germany by a deep-draught canal which English capitalists have proposed to construct between Kiel and some point on the Elbe.

The Austrian Government is resolved to improve the navigation of the Danube. The opinion prevails in that country that the removal of the obstacles in the Danube would enable Austro-Hungary to compete successfully with America in supplying Europe with grain. The rocks which are called the Iron Gates are to be destroyed by blasting, and rocky obstructions are to be cleared away in the channel of the upper Danube. The Bavarian and Wûrtemberg Governments show a willingness to co-operate with the Austrian, and so improve the river that barges can be towed throughout its whole course. The project of connecting the Danube with the Oder by a canal, which will enable the cereals of Austro-Hungary to be transported to the Baltic, is likewise a favorite one at Vienna. The scheme of digging a canal between the Dniester and the Vistula, and thus establishing a commercial highway between the Baltic and the Black Sea, is favorably entertained by Central European capitalists. The products of the South Russian grainregions could then be conveyed directly from Odessa to Dantzic, and shipped by way of the North Sea. The estimated cost of such a water-way is $100,000,000.

In France, Freycinet, when Minister of Public Works, instituted inquiries which led to the conclusion that in that country the business of transportation could be done by water-routes at from one third to two fifths the cost of rail

road conveyance. On the strength of this in formation the French Government resolved on the gradual improvement of harbors, rivers, and canals, the total expenditure determined on for this object being $200,000,000. The scheme of a ship-canal, connecting the Atlantic and the Mediterranean, to save the long and perilous voyage around the Spanish Peninsula, is still under consideration, and has good prospects of being adopted.

The Dutch have been stimulated, by the deflection of the Rhine-trade to Antwerp, to improve and expand their canal system, which has been for centuries the world's model. The States-General of Holland recently voted $1,250,000 for improving the canal from Rotterdam to the sea, and decided to cut a new canal from Amsterdam to Utrecht, and thence to the Merwede River, near Gorcum. The citizens of Amsterdam propose to construct another one between their city and the Waal, through the Guelon Valley. The Belgians are not disposed to yield up the prize without a contest. The canal at Charleroi is being widened, and a large central canal is to be dug through the whole breadth of the country. The Government is attempting to establish uniformity of gauge in the canals of Belgium. The great suspension-bridge across the East River, in New York, is nearing completion. The year has seen the approaches substantially finished and the work on the superstructure begun. Nearly all the floor-beams were laid before the close of 1881. The original plans were materially changed during the year, inaking the bridge five feet wider and four feet higher above the river, with greatly increased strength, to enable it to carry railway-trains of Pullman cars.

The tunnel under the Hudson is progressing rapidly and securely by improved methods, work going on from both shores. Steady progress has also been made in the excavations under Hell Gate for the removal of Flood Rock. Safety in the navigation of New York Harbor and adjacent waters has been largely enhanced during the year by the introduction of iron-hulled passenger and excursion steam

ers.

The renewal of the suspension-bridge at Niagara is a remarkable feat of engineering skill, as all the parts of the structure were removed and replaced with new, except the cables, which were repaired at the shore-ends, and a new anchorage was made, without any interruption of the railroad traffic. The fact that, after twenty-five years of use, the wire cables and suspenders of this gigantic span were found but very slightly impaired, is a gratifying proof of the security and durability of this type of structure. In 1877 Thomas F. Clarke examined a portion of the strands imbedded in the masonry, and found a few wires corroded. W. H. Paine shortly afterward instituted a more thorough investigation. Tests of the elongation of the cables under a given

moving load, and tests of single wires for tensile strength and ductility, were satisfactory. The strands were cleaned, freed from the wire bands, and opened, with the result of finding them as good as new, with the exception of the outer wires of the outside strands. As the shores were approached only the strands underneath were found to be affected. It was seen that the corrosion was due to the fact that the elongation and contraction of the strands under passing loads had loosened the cement from the outside strands, and allowed moisture to enter. The defective wires were cut out and new ones spliced in. The greatest number replaced at one end of any one cable was 65, the total number comprising each cable being 3,640. The examining commission recommended that the anchorages be re-enforced and that the iron superstructure of the bridge be renewed, and reported that the action of the cables indicated that they were in perfect condition. In the plan which was executed for the strengthening of the anchorages, one anchor-plate in each pit is made to answer for all the four new chains which were fastened, in addition to the old anchor-chains, two to the end of each cable. The new pit is beyond the two old anchorages. at the back of the old wali. The new anchor-chains connected with the upper cables pass in long links in a straight line from the point where they curve down to the anchor-plate to the end of the cables. The chains fastened to the lower cables pass from the same point, in still longer links, on each side of the old anchor-chains of the upper cable to the old lower cable anchorage, where they have to make an upward bend to join the end of the cables. This is secured by fastening the pins of the short links, which succeed to the pins of the old anchor-chain, by stirrups. The pits are 6 feet by 2 feet 6 inches. The anchor-plates are of cast-iron, 5 feet 6 inches square, and strongly ribbed. One pin passes through the plate and the whole eight links of the anchor-chains. The pits were sunk 17 feet deep on the New York side and 23 feet on the Canada side. The chamber for the reception of the plate at the bottom of the pits was 6 feet by 7. In filling up the pits no stone was permitted to come in contact with the chains. In renewing the iron-work of the superstructure, it was decided to use steel for the posts, chords, track-stringers, and lateral rods, and to make all other parts of iron. The new iron beams were first put in nearly throughout. The portion of the new work thus put in weighed 1,100 pounds per running foot. There were 150 feet of the new work finished at a time, which was equivalent, in the middle portions of the bridge, where the work was begun, to about 70 tons of extra dead load on the bridge. The weight of the wooden portions of the old bridge was estimated by John A. Roebling, at the time of completion, at 1,000 tons. Added woodwork and absorbed moisture are estimated to

have increased the weight to 1,228 tons. The new wooden structure, which has replaced it, is estimated to weigh 1,050 tons. A device is applied in the new superstructure for the automatic regulation of the continuous iron truss which is required to render the stays from the tops of the towers to the floors effective. It is necessary that the different points of this truss should remain as nearly as possible absolutely in the same position. The automatic adjustment by which the middle point of the continuous truss is kept from shifting at any moment toward either end, is effected by means of an iron rod stretching along the lower chord from one end of the bridge to the other. The rod is attached at each end to the short arm of a bent lever, at the other arm of which is suspended a narrow wedge. The wedge is held between the end of the chord and the abutment. The iron rod has the same measure of expansion and contraction as the chord, and the lever is so constructed that the wedge will be raised or lowered by the pressure or relaxation of the rod at each change in temperature, so that it will just fit in the space between the abutment and the chord of the truss, thus keeping the center of the truss absolutely stationary and the chord constantly rigid, while leaving full play for the elongations and contractions caused by changes in temperature.

A new iron light-house in Chesapeake Bay, off Cape Henry, is one of the finest structures of the kind. From base to top the height is 155 feet, the diameter at the base 30 feet, and at top 16 feet. There are six stories before reaching the service, watch, and lantern rooms and the roof. The total weight of materials is 1,700,000 pounds, 7,000 pounds of bolts being used in joining the parts. The structure has an octagonal frame of cast-iron and an interior of sheet-iron, cylindrical in shape. The castings of the base and first story are 2 inches in thickness. The sheet-iron lining is inch thick. The iron staircase goes around the cylinder. The light-chamber is a circular steel frame 12 feet in diameter and 9 feet high. The different stories are bolted together through the cast-iron floor-plates, which are 1 inch thick.

A larger proportion of the ships built on the Clyde in 1881 were made of steel than in former years. The year was one of remarkable activity. No fewer than 261 vessels were launched, with an aggregate capacity of 341,022 tons. In 1880, which showed the largest construction of any year since 1874, the tonnage reached 248,800. The number of contracts on hand gave indications of a still larger construction in 1882.

Professor Raoul Pictet, of Geneva, has been experimenting on an improved model for naval construction. He has worked out a design which differs essentially from the present type of hull, and which in the model promises performances in speed far better than the best

designed vessels are now capable of showing. He expects to attain a speed of thirty to thirtysix miles an hour. The advantage consists in such an arrangement of the keel as to diminish the resistance of the water to the lowest point. As the speed increases, the prow rises up, and only the sides of the hull and the portion in the vicinity of the wheel are subject to friction, so that the ship will glide over the water, instead of having to push its way through the water.

A new system of mountain-railroad has been invented by a French engineer, M. L. Edoux. It is being employed to establish communication between the watering-place of Cauterets and the baths of La Raillère, whose hot sulphur - springs are much visited by invalids. The springs are not quite a mile distant from Cauterets, and four hundred feet higher. The principle of the hydraulic elevator which is used in buildings is utilized, a mountain cataract furnishing the motive power. The car conveying the passengers is raised by five hydraulic elevators placed in towers some forty yards apart, each separate lift being eightyfour vertical feet. The top of each tower is a little higher than the foot of the next one, with which it is connected by an inclined bridge, along which the car is carried by gravity to the platform of the next elevator. The car descends to the station from the top of the highest tower, stopping on a platform which transfers it to the return-track by an automatic arrangement controlled by a hydraulic piston. The downward track winds around the side of the mountain at a very slight inclination, and ends at the second tower from the foot. The last two stages the car descends by means of elevators in the two lower towers and a connecting inclined track.

The inclined railway at the Giessbach, on the Lake of Brienz in Switzerland, is an application of the water-balance system. A descending carriage is made to draw up a second loaded one by means of a steel-wire rope connecting the two and passing over a reversing pulley at the summit, and of an excess of weight obtained from a load of water carried in a cistern in the under-frame. The length of the line is 1,100 feet, the height of the lift 303 feet, the average gradient 28 in 100. The car can carry forty passengers and luggage. It is provided with a toothed wheel and safetydrum. There is but one track, with double rails at the crossing point, the cars being able to turn out without switching from the fact that the wheels of one are flanged on the inside, and those of the other on the outside, of the rail. The weight of the car empty is 5.3 tons; loaded, it is from 6 to 9 tons, demanding a counterpoise of from 7.3 to 10-8 tons, requiring from 16 to 5·8 tons of water in the cistern. The maximum speed allowed by the charter is only one-metre per second. About one half of its length the track is carried on a wrought-iron bridge of arched trusses.

A plan has been adopted for a circular elevated railroad around the city of Vienna, to pass through all the suburbs and to connect with all the railroads entering Vienna. This will transform Vienna from the most deficient capital in Europe in facilities for local transit to one of the best-appointed cities in the world in this regard. Such a scheme can be carried out with less destruction of property in Vienna than in any other city. It will pass nearly the entire way through waste lands on the bank of the Danube Canal and the river Wien, and the long strip of common along the projected Gürtelstrasse Boulevard. The remaining portion passes through one of the old and squalid quarters of the city. The Franz Josef's Quai Park on the bank of the Danube Canal is chosen as the site of the central station. This is in the very center of the business part of the city. All the other stations are located with reference to street-traffic and the main arteries of circulation. Along the canal the line is carried over ground which is now unoccupied, on an elevated structure which is so high that the approaches to the bridges are in no way interfered with. It crosses the Stubenring on an ornamental viaduct to the left side of the river Wien. As far as the slaughter-house on the opposite side of the city from the central station the road is elevated throughout. Beyond that point it makes a sharp turn, and enters a cutting in the common-land of the Gürtelstrasse. Farther on it alternates between via ducts and cuttings, until near the Lunatic Asylum it is carried through a tunnel about 1,500 feet long. It then proceeds through an open cutting with retaining walls until it leaves the route of the Gürtelstrasse and enters the walls of the city again near the central station. The total length of the proposed Ring Railway is 12.844 kilometres, of which 7·572 is on viaducts supported by iron columns, 0.816 on masonry viaduct, 3-243 in cutting with retaining walls, 0-470 in bank with retaining walls, 0·449 in tunnel, 0.085 in covered cutting, and 0-209 on the level. There are in the plan 19 stations, of which 15 are elevated and 4 sunk. The line is to be double throughout. Branches are to be constructed to form junctions with all the railroad lines which converge at Vienna. The total length of the main circuit and branches together is about 28 kilometres, or 17 miles. In accordance with this plan, every railroad terminating at Vienna will be brought into communication, not only with the central station but with all the other railroads. It will give to each railroad, in addition to its own terminus, 19 stations in the circumference of the city. The present facilities for reaching Vienna by rail are inconvenient in the extreme, but this plan would render them superior to those of any other city. Every part of the city will in like manner be connected with all the other districts and with the railroads. The importance of the connection of the capital by this means with every railway in Austria from

a strategical point of view has commended the scheme especially to the military authorities. The maximum gradient is one in 60, the minimum radius 200 metres. In the neighborhood of the Danube Canal and the river Wien costly foundations will be necessary. It is proposed, where the foundations will be entirely hidden under the surface, to sink shafts, timber them inside, and fill them up with béton. The Stubenring and the approaches to the Tegethoff, Schwarzenberg, and Elizabeth bridges are crossed by ornamental viaducts in which the main girders are concealed by light cast-iron arches, so as to render the crossing of such important streets rather an architectural improvement than a blemish on the beauty of the city. The main span of the Stubenring viaduct is 80 feet, the height above the roadway 16 feet 10 inches.

The work on the Arlberg Tunnel is proceeding at a more rapid rate than was attained on the Mont Cenis or St. Gothard. The former was bored at the rate of 1,112 metres a year, the latter at the rate of 1,670, whereas the Arlberg is expected to be pierced at the rate of 2,160 metres a year. The cost as well as the speed of mountain tunneling has been affected by improvements in engineering. Owing to the technical advances, but in a large measure also to the comparative shortness of the bore, the cost per lineal metre of the Arlberg Tunnel is estimated at only $750, while the St. Gothard cost $1,250, and the Mont Cenis $2,000. On the Austrian side the same method of drilling employed in the other tunnels is used. The perforators drill twenty to twenty-five holes at one time, each 1 to 2 metres deep. They cover a space of seven square metres. With each blast the tunnel is lengthened 1 metre. The perforators move forward on wheels. The drills work with quick strokes, the impulse being imparted by compressed air at a pressure of five atmospheres, supplied through flexible tubes. The air is compressed by means of turbine waterwheels at the end of the tunnel. On the west side of the tunnel a new kind of perforator is being tried. The drills have each a diameter of 24 inches. They pierce the rock with a rotary action given them by means of a water pressure of from 60 to 100 atmospheres. These perforators, with six or eight drills, accomplish equal results with lighter charges of dynamite as the pneumatic perforators with their twentyfive or thirty chisels. After each blast the loosened material must be removed. The work of taking away the excavated material is of equal magnitude as that of boring the rock, and consumes as much time. The smoke of the explosion in the unventilated space makes it a difficult and dangerous task to remove the rubbish after each blast. The miners in the Arlberg have found that they can neutralize the ill effects of the poisonous air to a considerable extent by covering their mouths and nostrils with sponges steeped in vinegar. The work on the Arlberg Tunnel was commenced in June, 1880. By July, 1881, the east gallery

had been driven 1,010 metres, and the one on the west side of the mountain 710 metres. The tunnel is expected to be completed in five years from the commencement of the work.

The ventilation of long tunnels is a problem with which engineers have not yet dealt successfully. The natural mode of ventilation is the outflow of the warm air at the higher opening of the tunnel, and the inflow of cool air to supply its place at the other mouth. As the air within the tunnel is always warmer than the external atmosphere, natural ventilation takes place continually. Differences of temperature, of atmospheric pressure and moisture, and the direction of the prevailing wind, may increase the natural ventilation, or they may impede. A tunnel might be made with a sufficient difference of level at the two ends to insure complete ventilation, were it not that steepening the grade would necessitate the generation of more smoke, and thus aggravate the principal evil which it is sought to remedy. The ventilation of the Mont Cenis Tunnel is most imperfect, because unfavorable natural conditions of the external atmosphere almost neutralize the natural draught, notwithstanding the great difference of level at the two extremities, which is nearly 460 feet. The clouds of smoke which the engines leave in the tunnel roll backward and forward. The mechanical means which are employed to expel them are incapable of securing an effective ventilation. The air-compressing machines barely drive a current as far as the refugechamber sufficient to clear it of smoke; and the apparatus tried for pumping out the vitiated air has proved a comparative failure. The natural process of ventilation may be accelerated by either rarefying the air at the upper end of the tunnel, or by condensing it at the other. An artificial method of rarefying the air in the tunnel at the end where the current finds its natural egress has often been tried. Shafts are sunk into the tunnel at each end, and fires are kept burning to heat the air in one shaft, and thus cause an in-draught of fresh air through the other. One objection to this method for long Alpine tunnels is the expense of the apparatus and fuel when it is employed on such a large scale. Another objection is that the radiation of heat from the walls of the tunnel is so great as to render it desirable that the air should not only be renewed, but that it should be as cold as possible. The plan of cooling the air in the other shaft has not yet been tried. Wilhelm Pressel advocates employing this method instead of the other. He proposes to cool the air in one of the shafts by means of falling water. Mountain-streams of icy temperature are always accessible at the approaches of Alpine tunnels. He believes that a fall of about one hundred gallons a second through the shaft would cool the air sufficiently, and create a difference of temperature between the shafts sufficient to establish a current. A difference of 10° centigrade, he

thinks, would effect this object. The mouths of the tunnel and the openings of the shafts would have to be closed at will sufficiently to prevent the disturbing effects of wind on the ventilation. In cold weather the artificial refrigeration would be unnecessary.

The spiral tunnel at Leggestein, completed in the spring, was the first made and the principal one of a number of tunnels of the kind to be bored on the St. Gothard Railway. The plan adopted for the roads leading to the entrances of the great bore was to follow as far as possible the windings of the valleys of the Reuss, on the north side, and of the Ticino, on the south side of the mountain. This scheme of keeping in the valley-bottoms rendered it necessary to carry the line through considerable vertical distances by means of spiral tunnels, in which the gradient is steep and the curve sharp. The Leggestein Tunnel has a gradient of 23 in 1,000, and describes a curve of 300 metres. After leaving the tunnel, the railroad winds around the mountain, passing through a shorter tunnel above. The work of tunneling was exceedingly difficult, as the rock was hard granite, and, owing to the entire absence of water, the boring had to be done by hand. There are two other tunnels of this kind being bored in the Reuss Valley, that of Wellington, which is also bored by hand, and that of Pfaffensburg, each of which is 1,000 metres long. On the Ticino side there are four of these spiral or turn tunnels, from 1,500 to 1,600 metres in length.

The first passenger-train passed through the St. Gothard Tunnel on November 1st; time, fifty minutes. The tunnel exceeds the Mont Cenis Tunnel in length by 8,856 feet, being 91 miles long. Goeschenen, the northern end, is elevated 3,637 feet above the sea-level. The tunnel ascends in a gradient of 1 in 171 for 24,600 feet, and then 1 in 1,000 for 4,428 to the highest point, 3,785 feet above the sea. It keeps this level for 1,279 feet, and then descends with a gradient of 1 in 200 for 3,870 feet, and 1 in 500 for 13,792 feet. The station at Airolo is 3,755 feet above the level of the sea. The normal width of the tunnel is 24 feet 11% inches at the level of the rails, and 26 feet 3 inches, 63 feet above. The height is 20 feet. The roof is semicircular. The floor slopes with a fall of 23 per cent from each side to a drain 27 inches deep in the center. The line has also 52 subsidiary tunnels which, with the main tunnel, have an aggregate length of sixteen miles. There are 64 bridges and viaducts whose combined length form one per cent of the length of the line, while 17 per cent is taken up by the tunnels. The main tunnel is laid with two tracks of 4 feet 8 inches gauge.

The experimental works on the British Channel Tunnel have proved satisfactory. Two shafts were sunk on the English side, one at Abbot's Cliff, and one at Shakespeare Cliff. From the first a gallery was driven by ma