INTEROCEANIC SHIP RAILWAY. Capt. James B. Eads, the projector of a railway across the American isthmus for transporting ships, presented the essential features of his plan to the canal committee of the house of representatives in March, 1880. Of its.kind, the scheme is in many respects more ambitious than any heretofore proposed. The engineering and financial success achieved by rapt. Eads in the con struction of the St. Louis bridge, and the jetties at the mouth of the Mississippi river, demands a careful consideration of projects which he may advocate. The proposed railway is to consist of twelve tracks, placed 4 or 5 ft. apart, upon which the ship car riage, or cradle, rues. At each terminus an inland basin is excavated, perpendicular to the shore line of the harbor, and 3,000 ft. long. Gates placed at the outer end of the basin, which is lined with masonry, make it possible to pump out the water when repairs are necessary. The track in the basin is 30 ft. below water-level at the harbor end, and, rising 1 ft. in 100, intersects the surface level at the other extremity. The dimensions of cradles will be adapted to the size of vessel transported. The largest merchant ships weigh, when loaded, about 6,000 tons. This weight will be distributed over 1200 wheels, making the pressure 5 tons upon a single wheel which could support 20—a pressure ordinarily exceeded in practice, as the driving-wheels of many locomo tives must sustain 6i tons.
A ship to be transported enters the harbor end of the basin, and is floated to where her keel is over the keel-block of the cradle, then the supports are adjusted under the bilges substantially as in a dry dock. The weight rests chiefly upon the keel. while a part is distributed over the bilge blocks, which also keep the ship in an upright posi tion. A stationary engine hauls the cradle and ship out of the water, and then two very powerful locomotives are attached, which draw their great load to the other ter minus, at a speed of ten or twelve miles an hour. The locomotives are to have five times the size and power of freight engines, and with their tenders will use all twelve tracks. The wheels have double flanges, and as their number is great, the rails and road-bed sustain but a moderate pressure, and the failure of one or several wheels would not he serious. Derailment is impossible, and the displacement or breakage of rails would cause no delay, as six of them would bear the entire weight. Above each wheel are two strong steel springs, which diminish the. strain, and each wheel can be removed separately by loosening two bolts. Cars would pass each other by means of transfer tables, which would move the cradles sideways. One of the chief arguments against this plan is that loaded ships will not endure the strains imposed upon them when out of water, and supported only at intervals. The assumption that the mobility
of water equalizes the strain is not correct, as it is common in rough weather for the whole weight of a ship and cargo to bear upon the ends or the middle, leaving the remainder of the ship unsupported; indeed, a gale subjects a ship to very severe tor sional and lateral strains, which change constantly in direction and intensity—strains far exceeding any which would be incurred on the railway. Farther evidence upon this point is furnished by the portage railroad of the Alleghany mountains. which, forty years ago, connected the canal systems of eastern and western Pennsylvania. Over this railroad loaded canal-boats—frail craft compared with sea-going vessels— were hauled for a distance of over 30 m. lip and down steep inclines. Many experienced ship-builders consider ship transportation by rail feasible, and, compared with ship canals, ecpnomical. Thus it will be seen that this project involves only the combination upon tii large scale of a number of well-tried engineering expedients.
Routes could probably lie located at Panama, Nicaragua, and Tehuantepec, with a grade of 30 or 40 ft. to the mile. Capt. Eads estimates the cost of a road and harbor at Panama at $50,000,000, and the route the -shortest that could be found, but expensive harbor improvements would be required. The Chiriqui route has steeper grades, but superior natural harbors. The Panama route would probably exclude the transportation of vessels without steam-power. See INTEROCEANIC SHIP CANAL. Mr. Ends believes " that upon any route where it is possible to build a canal, it is equally possible to build and equip a substantial and durable ship railway," that railway is practicable where a canal is not; that the elements of cost, time of construction, speed in transit, capacity, and cost of maintenance and operating, are all heavily in favor of the railway; that the capacity of the railway could be increased at any time to transporn snore or larger ships with no interruption of traffic; that more accurate estimates can be made of the cost of a railway and the time of completion than of a canal, as the latter requires sub-aqueous work, where the conditions are more variable, and that, therefore, capitalists will have more confidence in the railway. It is estimated that the railway could be duplicated once in ten years for the interest on the difference between the cost of a canal and a railway of equal capacity. A traffic of 5,000,000 tons yearly, at $2 per ton, would give an income of $10,000,000, which, deducting 50 per cent for expenses, would leave a dividend of 10 per cent upon the capital.