Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/878

794 CANAL one lock will be required to get around each of the upper three dams. From the fourth dam to Grey town in the Caribbean Sea an independent canal will be required 41 9 miles in length with seven locks, which apparently presents no difficulty. The total length of the proposed canal is 61 7 miles, and no tunnel is required. The harbour of Grey- town has been partially destroyed by a silt which comas from the San Carlos, and others of the lower tributaries of the San Juan, and the branch of the river leading to Grey- town has become so much filled up that it is now, at the lowest stage of the water, only 324 feet wide and 6 inches deep at the fork. It is proposed to shut off this branch entirely and send all the silt-bearing water through the Colorado mouth, which empties into the sea 18 miles from Greytown, and to admit to the harbour only the water of the canal, which, being drawn from the main river above the mouth of the San Carlos, will be perfectly clean. The harbour then cleared out, will leave nothing to deteriorate it again. Short breakwaters will be required to protect the entrances from the surf, both of which are included in the estimate for the work. Careful gauging at the lowest stage shoAvs that Lake Nicaragua, which has a surface area of 2700 square miles, and a drainage area of 8000 square miles, will supply thirty- eight times the maximum p6ssible demand of water. The depth of water is to be 26 feet, the width at bottom 72 feet, and at surface 150 feet. The locks, twenty-one in CARIBBEAN SEA SAN JUAN (Creytov/ii. MERICA I PACIFIC OCEAN A B . Line of DarierrCanal C D . Une of Nicaragua Canal EF. Line of PanamaRailway 8J6 FIG. 12. Lines of proposed Darien and Nicaragua Canals. number, with a lift of from 8 to 10 feet, are to be 400 feet long and 72 feet wide. The estimate is stated at 15,900,000. M. Lesseps, in a lecture on the Suez Canal, delivered before the Societ6 des Gens de Lettres at Paris, has given it as his opinion that unless the Atlantic and Pacific can be united by simply piercing the Isthmus from sea to sea without kcks, as at the Suez Canal, the proposed scheme cannot possibly succeed as a commercial enterprise, because of the inadequacy of a canal with locks to pass the traffic that will frequent it, and also of the uncertainty of sufficient water to supply the lockage and evaporation. This latter objection, however, seems to be disproved by the researches of the American engineers who have investigated the sub ject. A further difficulty arises in maintaining a sufficient sea- water depth to the canal even after it has been formed. On this point the writer of this article, judging from docu ments prepared under the sanction of the Government of the United States and submitted to him by an authorized official of the Government, arrived at the conclusion that there are very formidable obstacles to the establishment and future maintenance of a deep-water entrance to the proposed Nicaraguan Canal at Greytown in the Caribbean sea. These obstacles involve the engineering problem of main taining permanent deep water through an extensive shallow foreshore composed of soft materials and exposed to heavy seas. The reports state " that at Greytown there arc now islands where twenty years ago there was water enough to float a frigate." It remains to be seen whether the same difficulties apply to the entrance to the proposed Darien scheme ; and, to show that such fears may not be un founded, we may remind the reader that the difficulties exist, as we have stated, at the Mediterranean entrance to the Suez Canal. The question as to the best route for transit between the Atlantic and Pacific is, it will be seen, still far from being solved, but the necessity for free access from sea to sea remains an acknowledged fact. Its importance, especially to the United States, but in some degree to all the world, is such that, great as are the engineering difficulties, this long-cherished bold idea may yet become a stupendous reality. (D. s.) Reference is made to the following works: Chapman, On Canal Navigation; Frisi, On Canals; Fulton, On Canal Navigation; Tatham s Economy of Inland Navigation; Valiancy s Treatise on Inland Navigation ; Principles and Practice of Canal and River Engineering, by David Stevenson, 2d edition, A. andC. Black, Edinburgh ; Report of the Secretary of the United States Navy for

1873