128 



NATURE 



[June i i, 1896 



crosses the line of the canal, it became imperative to in- 

 troduce locks on the Panama Canal, in order to endeavour 

 to complete the canal within a reasonable time and 

 at a practicable cost, the special advantage of the Panama 

 route disappeared. During the progress of the Panama 

 Canal works, the Nicaragua scheme naturally remained 



o3 



BRITO 



LOCKS ♦ TO S 



TOLA QAS'IN 



OCHOAtXAM 



V"SAN FRANCISCO BASIN 



GREAT DIVIDE 



. — Nicaragua Canal (longitudinal -^eciion). 



in abeyance ; but when the works at Panama came to a 

 standstill for want of funds in 1889, and discredit fell 

 upon the promoters, interest was again aroused in the 

 Nicaragua Canal as the only alternative method of con- 

 necting the Atlantic and Pacific. The two routes across 



the isthmus,'starting from points 2S0 miles apart on the 

 Atlantic side, present a remarkable contrast in their 

 natural configuration. The Panama route, starting from 

 Colon in the Bay of Limon on the Atlantic side, and 

 terminating near Panama in the Bay of Panama on the 

 Pacific coast, has a length of 46J miles ; and the ground 

 rises on the Atlantic side with a fairly gentle slope to the 

 central Culebra ridge, reaching a ma.ximum elevation of 

 about 317 feet above sea-level, and descends with a 

 steeper slope to the Pacific. The canal, as originally 

 designed, had to be formed in cutting throughout ; and a 

 considerable portion of the excavations had been accom- 

 plished along the 27 miles of lower ground at the two 

 ends before the cessation of the works, but comparatively 

 little progress had been made in cutting through the 

 main central ridge, 19 miles in width. The introduction 

 of five locks on each slope has very greatly reduced the 

 amount of excavation for carrying the canal through the 

 central high ground ; but it has been estimated that 

 nearly forty million cubic yards of excavation still remain 

 to be effected, and that an expenditure of ^36,000,000 is 

 required for the completion of the canal with locks. 



The Nicaragua Canal is designed to start from Greytown 

 on the Atlantic side ; and after traversing about twelve 

 miles of low marshy land, it is to rise by three locks to 

 its summit-level (tig. i). This summit-level is to consist of 

 dammed-up waters of the Deseado, San Francisco, and 

 San Juan rivers on the Atlantic slope, Lake Nicaragua, 

 from which the San Juan River issues, and the Tola basin 

 formed by damming-up the waters of the Tola and Grande 

 rivers on the I'acific slope. The canal is to descend by 

 three locks from the Tola basin to the harbour which is 

 to be constructed at Brito, by two converging breakwaters, 

 at the Pacific end of the canal. The peculiar feature of 

 the Nicaragua Canal is the long summit-level provided, 

 about 1 10 feet above mean sea-level, by damming-up the 

 rivers on each slope, in addition to the natural water-way 

 across the lake, thereby greatly diminishing the ex- 

 cavation for forming a canal with a total length of l69i 

 miles between the two oceans, and substituting free 

 navigation along 1424 miles of the route, in place of the 

 restricted navigation of a narrow canal (Fig. 2 ). In spite, 

 however, of the engineering skill exhibited in adapting the 

 design so as to take advantage of the special physical 

 conditions of the site, two high ridges have to be pierced 

 near the two extremities of the summit-level, known re- 

 spectively as the Eastern and Western Divides, involving, 

 in the case of the Eastern Di\ide, a mnximum depth of 

 cutting of 328 feet, equalling in depth the Culebra cutting 

 originally contemplated for a tide-level canal at Panama, 

 through strata apparently not very dissimilar to the 

 Culebra cutting, and exposed, as in that case, to an 

 e.xceptionally heavy tropical rainfall and a very unhealthy 

 climate. In addition to these unusually deep and for- 

 midable cuttings, a considerable amount of dredging 

 will be necessary along the upper part of the San 

 Juan River, to procure the requisite depth of 28 feet, 

 together with the removal of rock from its channel 

 at its exit from the lake and across some rapids in 

 its course. The formation of the canal across the 

 low-lying land between Greytown and the locks on the 

 eastern slope, presents no engineering difficulty ; but 

 the provision of a deep-water entrance between this 

 portion of the canal and the Atlantic, and its mainten- 

 ance, constitutes one of the most difficult problems of the 

 undertaking. Greytown, the only place along that part 

 of the coast, for a long distance, where deep water ap- 

 proaches the shore, is situated upon a lagoon which has 

 gradually formed in front of the port, by the advance of 

 the delta of the river San Juan under the influence of 

 the waves raised by south-easterly winds ; and it is pro- 

 posed to carry a breakwater out from the shore into deep 

 water to arrest the littoral drift, under the shelter of 

 which an approach channel is to be dredged. .-V dam, 



NO. 1389, VOL. 54] 



