Gambar halaman
PDF
ePub

way to be realized. The commission appointed by the United States Government to consider its feasibility, and select the best route, have presented a final report; and treaties are in progress with other countries concerning it. The Dutch have achieved a great engineering success in the completion of the North Sea Canal, which makes a seaport of the city of Amsterdam, floating the largest vessels, and allowing direct steamboat communication with foreign ports. The St. Gothard Tunnel is approaching completion; but its undertakers have been greatly dismayed by the discovery of an enormous miscalculation in the estimates of cost. Extensive and costly experiments upon the proposed railway-tunnel through the chalk-beds underlying the straits of Dover are undertaken, and will amount to a commencement of the work, if it shall be found feasible. In Italy we see the completion of an enterprise which has been pursued for many years, by which a large tract of land, submerged for ages, has been recovered to agriculture. Other similar works are proposed for the reclamation of the wide ranges of land which lie waste in that country, covered with disease-generating marshes; while in Holland a plan is seriously entertained by the Government for the draining and fertilization of the bed of the Zuyder Zee, which would increase the territory of that country about one-sixth, and afford a permanent revenue of millions of francs to the Government. The long-expected Russian railway across Central Asia has not yet been practically commenced, though the project is gaining favor. In our own country, the great works of river and harbor improvement, which have been carried on by the Government, are still under vigorous prosecution; the chief results of this year's labors have been the clearing away of Hallett's Reef, one of the most serious obstructions in the East River channel (see article HELL-GATE), and the deepening of the chief outlet of the Mississippi (see below).

The survey which has been conducted by the commission of the American Government for five years past upon the isthmuses of Panama and Nicaragua, with reference to a ship-canal, has been completed within the year, and final reports have been presented to the President. The route which was found most promising and practicable was one across the Nicaraguan Isthmus, by way of Lake Nicaragua. Four other proposed routes have been carefully examined. The one across the isthmus of Panama, formerly much thought of, was found to present the greatest difficulties. J. C. Trautwine, chiefengineer of the Panama Railroad, lately expressed an opinion that a canal over that route would cost not less than $300,000,000! The survey across the isthmus of Tehuantepec, ander Commodore Shufeldt and Engineer Fuertes, showed that the line proposed by those engineers by way of the river Coatzacoalcos would require the construction of as many as 140 locks, which, in connection with

the deficient water-supply, was enough to condemn the plan. The route between the gulf of San Blas and the river Chepo or Bayanos has been supposed to be a specially desirable one, because the tides from both oceans are nearer together at this point than elsewhere; but the survey revealed insurmountable difficulties, even after an eight-mile tunnel should have been cut. A survey from Caledonia Bay out discovered no pass at a less elevation than 1,000 feet. Several other routes which were surveyed showed difficulties still more formidable. The Government has expended about $60,000 in this investigation.

The treaties with foreign powers are to be made on the basis of the Clayton-Bulwer Treaty of 1850, guaranteeing the neutrality of the canal. The estimate of the cost returned by the commission is $65,722,157; but several practical engineers, who have examined the route, conjecture that obstacles will be encountered which will increase the cost to nearly $100,000,000. The work cannot be completed in less than five years of hard labor; but if it is sustained by the leading governments, it is supposed that it will not be delayed or abandoned for want of funds. The distance to be excavated is 614 miles, and the total length of the canal, including 53 miles of slackwater navigation, by way of the San Juan River, and 56 miles across Lake Nicaragua, will be 1804 miles from ocean to ocean. For a number of years there has been a considerable and increasing transportation traffic by the way of Lake Nicaragua and the San Juan River. Whether a ship-canal across the Nicaraguan Isthmus would draw any of Europe's trade with the East from the Suez Canal is doubtful; but the benefits it would afford to the American trade with the East and the Pacific coast, and the improved communication it would render between the western side of the North and South American Continents, and the whole commercial world, would be much more than commensurate with its cost.

An American engineer, Henry C. Spalding, has broached a scheme for letting the waters of the Black Sea into the Caspian through an artificial channel-way, thus greatly enlarging the area of the latter sea by the submersion of comparatively sterile tracks, but immensely improving the fertility of the surrounding regions, and giving Russia maritime communication with the commercial world, and a broad sea-coast. His project is to cut a canal, 150 metres wide, from a point in the basin of the Caspian Sea, which is 15 metres below the level of the Black Sea, in a westerly direction to such a point that it will have a depth of 10 metres; from there a narrower cutting is to be carried on to the Black Sea. This narrower channel, he calculates, should have a depth of three metres where it strikes the Black Sea, and a width of 50 metres; through this the water would flow with a velocity of 12 kilometres an hour, and, where it gives into the larger

channel, would have a fall of 10 metres, which would give it a tremendous excavating power. It would take about six years, he reckons, to complete the excavations, and then about forty years for the waters of the two seas to approach near enough to a level to allow of navigating the canal. This time can be shortened to twenty-five years, he further proposes, by connecting the rivers Don and Volga through another cutting.

The scheme of letting the waters of the Atlantic into the desert of Sahara is gaining favor. M. de Lesseps has expressed his opinion that it can easily be realized, and advocates also the connection of the Congo and Zambesi rivers by a canal at the point where they approach each other within eighteen miles, both being navigable at that point. He considers that the climate of Europe would be improved, if anything, after the submersion of the desert, and suggests that the fertile oases are all above the ocean-level.

Reports on the improvement of the mouth of the Mississippi show that the work is progressing, and that satisfactory results have already been attained. Grand Bayou has been closed, and the water which passed through it now makes its way through the pass, increasing the current and its scouring force greatly. The width, depth, and straightness of the channel are improved, and a recent statement of Captain Eads shows an average depth of 20 feet through nearly the whole length, the exceptions being a spot near the upper end of the pass, and one within 1,000 feet of the lower end of the jetties, about 75 feet together, where the depth is 19 feet in the shallowest places. Captain Eads declares that the alluvium carried out of the pass on the jetty system is not deposited so as to form a new obstruction outside; but that, on the contrary, a large lump at the mouth of the South Pass has been cut through by the increased strength of the current, and is being gradually worn away. A series of dikes and wing-dams is in process of construction in the pass above the jetties, which is intended to reduce the width of the channel gradually from 5,000 to 800 feet, and accelerate the scouring out of the

pass.

The Dutch opened the new North Sea Canal, in the summer of 1876, amid festal rejoicings. This canal, although but fourteen miles long, is of immense utility to the commerce of the country, and of the highest importance to the prosperity of Amsterdam; and its construction was attended with such difficulties as to place it among the highest order of engineering achievements. A great part of its course is over tracts which were submerged by an arm of the Zuyder Zee, and had first to be pumped dry to allow the bed of the canal to be dug

out. To prevent the sand-hills near the sea from choking the canal, huge locks had to be constructed. One of the locks is 315 feet long and 59 wide, and another ship-lock is 239 feet

by 46; and both are built upon no fewer than 8,896 piles. The tremendous driving force of the storms on the North Sea, and the shifting sands of the coast, gave rise to difficulties which taxed all the resources of engineering skill. The plans of this great work were devised by the English engineers Sir John Hawkshaw and Darnton Hutton. The canal receives vessels of any tonnage. At intervals it is enlarged into basins like the Suez Canal.

The plan for draining the Zuyder Zee was pronounced practicable and advisable by a Government commission in 1873. During the last couple of years it has been much discussed in the Legislature, in the chambers of commerce, and by the press; and there seems every likelihood that its practical execution will soon be commenced. The most difficult part of the work will be the construction of a great dike across the lake, from the town of Enkhuisen to the island of Urk; and then, with two angles, to Kampen, on the east side. The length of the dike is to be 40 kilometres, some 25 miles, with a height of 8 metres, or 26 feet, above high-water level, and a breadth of 50 metres, or 164 feet. Double sluices at Enkhuisen, Urk, and Kampen, will communicate with the sea. Alongside of the dike a canal will be made on the inside, and on the interior berm will be the tow-path and a railroad. The plan for draining the lake is to divide it into squares, which are to be successively pumped out by immense steam-engines into canals of discharge, which will convey the water into the large permanent canals of maritime communication, leading into great reservoirs, from which the accumulated water will flow out at low tide. Large commercial canals will be constructed between the harbors now situate upon the lake, of dimensions approaching those of the new North Sea Canal from Amsterdam. The largest of the canals will be one from Enkhuisen to Amsterdam, and one starting near Harderwyk, and going along the southern shore to Huisen, then turning toward the Pampas, and joining the other line. Of the smaller order of canals, there will be four principal lines, two parallel, running southwest and northeast across the bed of the lake, and two intersecting ones. For the completion of the drainage, thousands of small trenches and ditches must be cut over the entire bottom in every direction. The construction of bridges and sluices will present greater difficulties than the work of canalization. Three several kinds of sluices will have to be made the great double sluices at Urk, Enkhuisen, and Kampen; and a score of others of the same construction at all the crossings of canals, the simple sluices for the outflow of water, of which there will be three by the side of the three great double sluices, and the small sluices for irrigation, of which there will be great numbers distributed over the entire surface of the reclaimed lands. The mean depth of water to be drawn off is es

timated at 3 metres. If 9,400-horse power is applied it is calculated that the lake will be drained in about two years, at the rate of 4,500 cubic metres per minute. The only efficient power here applicable is supposed to be the steam-engine. After the steam-pumps have done their business, dredges will have to be employed to dig out the bottoms of the canals, and clear away the mud, where large structures have to be built. For the foundation of many of the heavy structures it will be necessary to sink piles and bundles of fascines, as has been done in the making of the great Amsterdam Canal. The entire work, it is estimated, can be completed in from twelve to sixteen years. The surface drained will be 196,670 hectares, or about 795 square miles, of which area about one-tenth will be taken up by roads and canals. It is supposed that, with all allowances, there will be about 150,000 hectares of fine, tillable land. The expense of the undertaking is estimated at 240,000,000 francs, a large estimate, exclusive of interest. If the Government should carry out the undertaking, as seems most likely, it is calculated that it would bring in, after completion, an annual revenue of 1,880,000 francs.

Two enterprises for the reclamation of large submerged tracts are successfully in progress in Italy. The Ferrara Marshes, in Northern Italy, are being drained by means of steampumps, constructed by John and Henry Gwynne, of Hammersmith, England. The area to be reclaimed is 200 square miles. The engines lift 2,000 tons of water per minute through an average distance of seven feet three inches. The maximum lift is twelve feet. The water is discharged into the river Volano, at Cordigoro. Another large enterprise is the drainage of Lake Fucino, which lies about 55 miles east of Rome, and has an area of sixty-one square miles, by means of a siphon 1,500 yards long, from canals which have been dredged out at the bottom. The works have been going on many years, at the expense of the late Prince Torlonia, and the enterprise will soon become remunerative. This area was drained by the Emperor Claudius, and the ancient works were suffered to go to decay in the middle ages. The project was at first designed to restore the Roman works, and a company was formed in 1855 for that purpose, and the work was intrusted to M. de Montricher, a well-known French engineer. This was found impracticable, and, the Prince Torlonia assuming the entire responsibility, the present works were constructed. About 50,000,000 francs have been expended upon them thus far.

There are suggestions of extensive improvements in the harbor of Genoa, and various plans have been proposed for the work. It has long been the dream of the Genoese to make their harbor the best in the Mediterranean, and regain their ancient commerce and prestige on the seas. A nobleman of Genoese birth, it is said, has presented the city with the sum of

20,000,000 francs, to be devoted to harbor improvements.

The tunnel under the English Channel, for the commencement of which companies have been formed in London and Paris, it is proposed to construct on the route proposed by Sir John Hawkshaw, from St. Margaret's Bay to a point near Sangatte on the French coast. In this course it is expected that it will pass through chalk-beds the entire way, while in the route proposed by M. Thomé de Gamond it is known that several different strata would be encountered. The distance across the Channel in the proposed course is 22 miles, which, with the long approaches necessary, would make 31 miles altogether. Shafts are to be sunk on either shore to the depth of 450 feet below high-water mark. At that depth driftways are to be driven, which will serve for the drainage of the works when in progress, and of the tunnel permanently. The tunnel will commence 200 feet above the driftway, with an inclination of one foot in eighty down to the junction with the driftway, and then of one foot in 2,640 to the centre of the Channel, where it will meet that driven from the other side. The dimensions of the tunnel will be those of an ordinary railroad-tunnel for two tracks. A driftway, nine feet in diameter, it is proposed first to carry entirely through, which can afterward be enlarged to the size of the tunnel. A machine for tunneling in chalk has been invented by Dickenson Brunton, an English engineer, which has been successfully tried upon the bed of gray chalk through which the tunnel is to be made. It works similarly to an ordinary board-auger, cutting off the chalk in slices, which fall upon an endless band, and are loaded upon wagons. The machine, it is found, can cut a driftway of seven feet diameter at the rate of something over a yard an hour. At that rate it would take two years to complete a driftway under the Channel with a machine starting from each side. The expense of completing such a driftway is estimated at £800,000, including interest upon the outlay. Engineers and contractors of experience have calculated that, after the driftway should be completed, it would take four years' time and £4,000,000 only to enlarge it to the dimensions of a raiload-tunnel, and to construct the junctions with the railways on either side. It seems certain now that the commencement of this work will soon be made and its practicability tested. The companies which have been formed for this purpose are to unite with the French and English railways interested, and with the Rothschilds of London and Paris, in making up the sum of £160,000, to be expended upon sinking a shaft on either side to the depth of 450 feet, and driving a headway a short distance under the sea.

The project of a tunnel under the North River from New York to Jersey City, for railway transportation, for which a company was formed some time ago, gave rise to a long

contention in the courts with the Delaware & Lackawanna Railroad Company. The tunnel company has come out victorious in the litigations, and nothing now lies in the way of the enterprise. The works were begun a long time ago, and now will probably be pushed forward to a speedy completion. The capital stock of the company is to be $15,000,000, of which, it is said, $10,000,000 has already been subscribed; Senator Jones, of Nevada, is said to be an active promoter of the enterprise. The project was first advanced by D. C. Haskin, of New York, who is the president of the corporation. The beginning of the work was the sinking of a vertical shaft lined with brick masonry of three or four feet thickness, having a diameter of 30 feet, in Jersey City, at the junction of Jersey Avenue and Fifteenth Street. When the shaft shall have been sunk to the depth of 65 feet, the horizontal cutting will be commenced. The direction of the tunnel will be northeast and southwest. It will have a length of about two miles; the terminus on the New York side will be near Washington Square. It will descend from both ends toward the centre in a gradient of two feet in 100. The diameter of the tunnel is to be 26 feet. Its roof will be nowhere less than 35 feet below the bottom of the river, so that there will be no danger from the anchorage of vessels. Little blasting will be required, and the two or three veins of rock which will have to be penetrated are of soft substance; the first vein of rock to be encountered crops up about 1,100 feet from the New York side. After a few feet of the lateral tunnel shall have been excavated, an iron cylinder will be introduced, in which the workmen will be protected when driving forward the tunnel. The cylinder will have hinged doors, and be provided with an apparatus and tubes for introducing compressed air from the surface.

There is a proposal to carry a telegraphic wire across the African Continent, from Khartoom, where there is telegraphic communication with Alexandria, at a distance of 1,100 miles, to Delagoa Bay, the terminus of the Cape lines. The distance between these points is 2,300 miles; but extensions are in progress which will shorten it to 1,500 miles. It is suggested that the trees might be utilized as telegraph-poles, and that depredations of the natives, who might covet the valuable iron of the wires, might be prevented.

The Dutch Government have issued proposals for the improvement of the harbor at Batavia, the capital of the island of Java and of their East Indian possessions. The only communication between the town and the present harbor, which has an excellent roadstead, has been by a canal 8 or 10 feet deep at low tide. The present accommodations are entirely insufficient for the large steamers which are employed in the Oriental trade, since the opening of the Suez Canal. It is therefore proposed to construct a new harbor

at Tandjong-Priok, to be formed by two breakwaters, 1,963 and 1,743 metres in length respectively, and rising 2 and 13 metres above low-water mark, with two inner harbors, of which only one is to be constructed for the present, each having a length of 1,100 metres, and a basin 7 metres deep and 175 metres in width. The entrance to the outer harbor will be 250 metres wide and 8 metres deep at low water. There will be 1,500 metres of quay, and a channel 50 metres wide leading to a coaling station. Between the harbor and Batavia a canal, five miles long, and a railroad, are to be built. The cost of the entire works will be $15,000,000; but for the portion to be constructed forthwith the estimate is something more then half that amount.

The first wire carried across between the towers of the Brooklyn Bridge was fastened on the 22d of September. This great work, after seven years of labor and the expenditure of $6,750,000, is still a long way from completion. The entire estimated cost of the completed structure is now set at about $11,250,000, or more than double the original estimate.

The contract for the construction of the proposed railroad-bridge at Poughkeepsie, over the Hudson River, has been taken by the American Bridge Company, of Chicago. The main part over the water will consist of five spans of 525 feet each between the centres of the piers, whose breadth will be 25 feet. The bridge will be of the description called the undergrade or deck bridge, and will have two tracks and sidewalks, and an under and upper deck, the latter carrying the two railroad-tracks, and the other a carriage-way of 16 feet clear width. Each span is to have two trusses, 25 feet between centres, of the rectangular description, with double intersections; the material will be iron and steel combined. The trusses are to be 58 feet high, and the top of the piers 135 feet above high-water mark, so that the elevation of the track above the river at high tide will be 193 feet. The approach on the west side of the river will have one span of 160 feet, formed by two trusses, 30 feet in height. The long approach on the other side, extending across the town, will be composed, as far as Water Street, of iron trestling, formed by three post-bents strongly braced, and four lines of stringers of iron lattice, making spans of 20 to 60 feet. Across the Hudson River Railroad grounds, Water Street and Dutchess Avenue, will be two spans of 25 feet depth. Beyond, as far as the oppo site side of Tallmadge Street, where the approach ends, will be iron trestling, except at the crossings of Tallmadge and Delafield Streets, over which will be made two 90-feet spans. The entire length of the bridge and approaches will be 4,500 feet. The plan of the bridge proper is a suspended girder, with parallel and cradled cables, and two decks. The girder, 1,680 feet in length, will be of wrought-iron. The supporting towers will also be of wrought

[merged small][merged small][graphic][ocr errors][merged small]

track will have eight columns 80 feet high and 11 feet in diameter. Each chamber in the lower tower will have twelve saddles and two pairs of compensating levers. These and their attachments will be carried by a frame that extends in both directions across the saddlechambers and over the heads of all the columns of the tower. All the parts of the saddles and the lever attachments for the stay system will be worked in together upon this frame; and so that the parts will move together sufficiently to compensate the expansion and contraction of the main back-stays beyond what the tower itself sustains. The saddles will move by steel rollers upon steel faces under the carryingframe. The anchorage of the cables will be in the solid rock at both ends. It is expected that this bridge will pave the way for a new railroad to the West, with a route between New York and Chicago only 921 miles long, a saving of 50 miles over any existing line.

A new bridge is to be constructed at Montreal, about four miles from the Victoria Bridge, which is to be called the Royal Albert Bridge, and will be the longest structure of the kind in the world. Its whole length, including the portion built over the land, will be 15,500 feet, almost exactly three miles. It will start from the level of Sherbrooke Street in Montreal, and pass through the town at the height of about 90 feet, with distances of 150

VOL. XVI.-17 A

to 200 feet between the piers. Between the city and St. Helen's Island, whose centre is of the same elevation as the roadway of the bridge, there will be six spans of lattice, one of 550 feet and the rest of 300 feet. The roadway will have but a single track; but on the island side-tracks and a crossing-station will be made. From the centre of this island to the water's edge four spans of 240 feet will be required. On the other side of the island there will be twenty-one spans of 200 feet to the other channel, and over that five spans of 200 feet, the roadway on this side having a falling gradient of 1:100. On the lower side of the river embankments will be made, and connections established with the Montreal, Portland & Boston, and the Grand Trunk Railroads. At the other end there will be a junction with the Quebec, Montreal, Ottawa & Occidental Railway; the distance between the two junctions is five and a half miles. In the navigable channel the piers, which will be like those of the Victoria Bridge, with heavy ice-breakers, will have to be put down with caissons, in a channel 40 feet deep, where the current is sevenmiles an hour. The superstructure will be of iron lattice-work, each pier being crossed by four girders, placed 18 and 14 feet apart; between the inner girders will be two street-car tracks; between them and the outer girders will be the roadways for teams, and on pro

« SebelumnyaLanjutkan »