National Geographic : 1899 Jul
PHYSIOGRAPHY OF NICARAGUA CANAL ROUTE 237 Lake Nicaragua has a regular oval outline, its longer axis extending about northwest-southeast. Its area is very nearly 3,000 square miles, and the mean elevation of its surface is about 104 feet above tide. Its shores present considerable diversity, depending chiefly on the character of the rocks which form them and the direction of the prevailing winds. The trade winds blow with great persistency throughout a large part of the year. They are deflected from their normal course by the high volcanic range of northern Costa Rica, so that instead of being northeast winds they vary from east to east-southeast. As a result of this constant wind direction the southeastern end and northeastern side of the lake rarely experience any surf, and hence those portions of the lake shore have no beach, but are bordered by swamps, with vegetation constantly encroach ing upon the lake. Along the southwestern side and western end of the lake, on the other hand, there is a constant heavy surf and as a result a broad sand beach, generally backed by a wave-cut cliff. The accompanying map (page 239), based upon surveys made by the U. S. Nicaragua Canal Commission, shows the configuration of the lake basin. The most interesting fea ture shown is the old channel, evidently a drowned river chan nel formed when the southern half of the lake basin was dry land. This channel marks the course of a river formed by the union of the several streams now entering the lower end of the lake with the one which occupies the upper portion of the San Juan valley. It is first detected in the vicinity of the Solenti name islands, and if it was ever excavated between this point and the mouth of the Frio this portion has subsequently been filled by sediment brought into the lower end of the lake. From the Solentiname islands for about 10 miles northwestward there is only a slight indication of the channel. Thence to the base of Madera it is continuous and distinct. The greatest depth in the lake, over 200 feet, is near the western end of this channel. To the west of the bay, which, as shown on the map, plate 6, formerly indented the Pacific coast, was a long cape or peninsula. This now forms a part of the narrow strip of land occupied by the continental divide between Lake Nicaragua and the Pacific. This part of the isthmus, although intimately connected with the Nicaraguan depression, is not properly a part of it. Its to pography is particularly interesting in connection with the pro posed canal, since it contains the lowest gap in the continental divide between the straits of Magellan and the Arctic ocean.