This line, then, runs through the valley of the river Lajas, the waters of a principal branch of which interlock with those of the Rio Grande, and, through the valley of the latter, reaches the sea. The stream first named has its origin about ten miles south-westerly from its entrance into the lake, on the eastern slope of the dividing ridge, and after running north-westerly two miles, along the base of the hills, takes a northerly direction through comparatively level savannas, a distance of six miles or eight miles, when it bends to the east, and in a mile and three fourths enters the lake. The Rio Grande rises on the eastern slope of the same range of hills, and two or three miles north-west from the sources of the Lajas, and, after flowing some three or four miles at the foot of their slope, bends to the west, and by a narrow and somewhat irregular valley passes through the ridge, and thence, in a more capacious and uniform valley, into the Pacific.
Western Section of Proposed Canal between Lake Nicaragua and the Pacific.—The entire line of the canal proposed by Colonel Childs, and upon which all his calculations and estimates are based, is therefore through the valley of the river San Juan into Lake Nicaragua, across Lake Nicaragua to the mouth of the Rio Lajas, through the valley of that stream, and across the summit of forty-seven and a half feet which separates it from that of the Rio Grande, and down the valley of the Rio Grande to Brito, where that stream enters the Pacific.
Now, in order to understand Colonel Childs' conclusions, and appreciate the data which he gives, we must know what kind of a work he proposes. He contemplates a canal but seventeen feet deep; and as he intends to supply the western section, from the lake to the sea, by water from the lake, it would be necessary to commence construction in the lake at a point where the water is seventeen feet deep at mean stage. This point is opposite the mouth of the Lajas, and twenty-five chains from the line of the shore. From this point, for a mile and a half, partially along the river Lajas, the excavation will be principally earth; but beyond this, for a distance of five and a half miles, which carries the line beyond the summit, three fourths of the excavation will be in a trap rock. That is to say, the deepest excavation, or open cut, will be sixty-five feet, and involve the removal of 1,879,000 cubic yards of earth, and 3,378,000 cubic yards of rock. The excavation and construction in this five and a half miles alone are estimated at upward of $6,000,000.
The summit passed, and the valley of the Rio Grande reached, the excavation, as a general rule, will be only the depth of the canal. Colonel Childs found that the lake, at ordinary high water, is only 102 feet 10 inches above the Pacific at high and 111 feet 5 inches above it at low tide, instead of 128 feet, as calculated by Mr. Baily. This descent he proposes to accomplish by fourteen locks, of eight feet lift each, placed at proper points in the valley of the Rio Grande, thus bringing us to Brito, the terminus on the Pacific.
The harbor of Brito, as it is called, or the point where the Rio Grande enters the sea, is at best only a bad anchorage. There is here a small angular indentation of the land, partially protected by a low ledge of rock, but nothing adequate for the terminus of an important work like the proposed canal, or capable of answering the commonest requisites of a port. To remedy this deficiency, Colonel Childs proposed to construct an artificial harbor, of thirty-four acres area, by means of moles and jetties in the sea, and by extensive excavations in the land. If, as he supposes, the excavations here would be in sand, it is obviously almost impossible to get proper foundations for the immense sea-walls and piers that would be necessary for a work of this kind. On the contrary, if these excavations should be chiefly in a rock, as seems most likely, the cost and labor would almost surpass computation. Assuming the excavations for the purpose to be in earth and sand, Colonel Childs estimates the cost of making a harbor at a little over $2,600,000.
Middle Section of Proposed Canal—Lake Nicaragua.—Proceeding from seventeen feet depth of water in the lake, opposite to the river Lajas, in the direction of the outlet of the lake at Fort San Cárlos, there is ample water for vessels of all sizes for a distance of about fifty-one miles, to a point half a mile south of the Boacos Islands. Here the depth of water diminishes rapidly to fourteen feet. For the remaining five and a half miles to the fort, the water is variable, averaging only about nine feet at low and about fourteen at high water. For this distance of five and a half miles, therefore, an average under-water excavation of eight feet would be required to make the channel, at low water, of the depth of the canal, or seventeen feet. But if the lake were kept at high level, the under-water excavation would be but an average of three feet.
Colonel Childs proposed to protect this portion of the channel by rows of piles driven on each side, along its whole extent, and thinks, after the excavation were made, a sufficient current would be established to keep the channel clear.
THE RIVER SAN JUAN.
Eastern Section—The River San Juan.—We come now to the section between Lake Nicaragua and the Atlantic, through or along the river San Juan. Excepting a small settlement at the Castillo Viejo, at the Castillo Rapids, thirty-seven miles from the lake, the valley of the San Juan is wholly uninhabited. This section, hitherto supposed the easiest, is, nevertheless, by far the most difficult part of the proposed enterprise.
Colonel Childs carried a line of levels from the lake at San Cárlos to the port of San Juan, on the northern bank of the stream. The whole distance from San Carlos to seventeen feet depth of water in the harbor of San Juan is 119⅓ miles; and the whole fall, from the surface of high lake to the surface of highest tide in the harbor, is 107½ feet—to lowest tide, 108¾ feet.