Lake Nicaragua is estimated by Colonel Childs to be one hundred and ten miles in extreme length by thirty-five in (average) width. Its nearest approach to the Atlantic is at its southern extremity, from which, on a right line, it is about eighty miles distant. The point of its nearest approach to the Pacific is near the middle of its length, where, by the shortest line, the distance is about eleven miles.
The San Juan River was found by Colonel Childs to be, following its sinuosities, 119 miles in length. It has a great number of tributaries, generally small, with the exception of the San Cárlos and Serapiqui, which come in from the mountains of Costa Rica on the south. The first of these enters the San Juan at sixty-five miles, and the second ninety miles below the lake. These streams flow through valleys transversely to that of the San Juan, which is further intersected by ranges of hills, coming in both from the north and the south, at the Rapides del Toro, Castillo, Machuca, etc.
The lake of Nicaragua lies longitudinally, nearly parallel to the Pacific Ocean, and is separated from it, for nearly two thirds of the length of the lake, by hills of comparatively moderate acclivity and elevation, in most cases capable of cultivation to their summits. Within this distance, also, are several transverse valleys, extending nearly (Colonel Childs says quite) across, with summits varying in height, and furnishing generally good opportunities for direct communications by ordinary roads or by canal.
Route via River Sapoa.—This line lies chiefly in the department of Guanacaste, now in dispute between Nicaragua and Costa Rica, and actually occupied by the latter.
The examination of this line by Colonel Childs only proved its impracticability for the purpose of a canal. He found that to pass the summit a cut 119 feet in depth would be required, and an up-lockage from the lake of 350½ feet, and a down-lockage to the Pacific of 432 feet. Water to supply the upper locks, it was ascertained, could only be obtained with difficulty, and at great cost. Besides, a long rock cut of three fourths of a mile would be required from low-tide mark in the bay of Salinas to deep water. In short, the physical difficulties on this line, if not of a nature to make the construction of a canal impossible, were nevertheless such as to make it impracticable.
Route from Mouth of the Rio Lajas to Brito.—The line from Lake Nicaragua to the Pacific, to which public attention has been most directed, is one starting from the mouth of the Rio Lajas, a few miles below the town of Rivas, or Nicaragua, to the port of San Juan del Sur, or Concordia, on the Pacific. As already stated, not less than three surveys had been made over this line; one in 1781 by Galisteo, a Spanish engineer, and the last by Mr. Baily, an Englishman, under the republic of Central America, published in Stephens' Incidents of Travel in Central America. The line pursued by both Galisteo and Baily was governed by the circumstance of a measurably good port on the Pacific—that of San Juan del Sur, the best on the whole line of coast from the bay of Salinas northward to Realejo. Baily's line is sixteen miles and 730 feet in length, and the greatest elevation above the lake 487 feet. That of Galisteo is seventeen miles 200 feet in length, and the greatest elevation above the sea 272, and above the lake 134 feet. Baily's line, for half of its distance, involved 209 feet of average vertical cutting; that of Galisteo, for half of its length, an average vertical cutting of 108 feet. These facts, and others, among which the absolute impossibility of supplying the summit levels with water, and the necessity of tunnels, combined to make the construction of a canal on this line wholly impossible.
EXPLORING FOR A LINE.
Colonel Childs seems to have been satisfied of the impracticability of this line, after a very rapid examination, and to have devoted himself to the discovery of one more feasible. In doing this, however, it was found necessary to abandon San Juan del Sur as the western terminus.
Starting at the point on the lake to the eastward of Rivas, levelling westward, through a transverse, moderately undulating plain, he ascended, on a distance of six and a half miles, 326 feet, to the summit of a broad valley, passing between the hills (which are here of moderate height), and connecting with another valley on the west side, which extends to a place on the Pacific called Brito, where a stream, named Rio Grande, flows into the sea. The quantity of water available for this summit being entirely inadequate, and the cut altogether too formidable, on the plan of carrying through the level, this route was abandoned. Another line, not far from this, was attempted, with very nearly the same result.
Colonel Childs next started from the mouth of the Rio Lajas, the same point with his predecessors, and carried a line of levels to the summit of a transverse valley lying about six and a half miles south of Rivas, and reaching between the valley of Rio Lajas and that of the Rio Grande, already mentioned as flowing into the Pacific at Brito. This summit was found to be only forty-seven and a half feet above the surface of the lake, as it stood on the 23d day of December, 1850, at which time it was three and a half feet above its lowest stages, and one and a half feet below the level at which it ordinarily stands at the height of the rainy season. The length of this line from lake to sea is about twenty miles. This is the route, and the only direct one, between the lake and sea, regarded by Colonel Childs as feasible, and upon this all his calculations respecting the proposed canal are based. In his own language: 'The conclusion was arrived at that the line leading from the lake, at the mouth of the river Lajas to the Pacific at Brito, presented more favorable conditions for the construction of the canal than any other; it was therefore determined to survey and carefully to locate a line across upon this route.'