Between Cuajiniquil, two and one-fourth miles east of Rio Sapoa, and Tortuga, six miles further east, are the little streams, Lapita, El Cangrejo, Puente de Piedra, La Vivora, Guabo, Genizaro and Tortuga, the latter the greatest in volume, being about one hundred and sixty feet wide at its mouth and navigable. In the further distance of seventeen miles going east, we cross the rivers Zavalos, Cañitas, Quesera, Mena, Mico, Sapotillo, Quijada, Quijadita, Santa Barbara, Sardinia, Barreal, Cañas, Perrito and, finally, Las Haciendas which is navigable by small boats. From here to San Carlos, at the outlet of Lake Nicaragua, the distance is sixty-four kilometers, and the principal rivers which cross this tract are El Pizote, Papalusco, Guacolito, Zapote, Caño Negro and Rio Frio. The Rio Frio is of considerable magnitude, and with its many branches drains a large area of the territory lying on the slopes of the volcanoes of Miravalles and Tenorio. It pours much sedimentary matter into Lake Nicaragua, and has thrown an extensive mudbank across the lake entrance to the River San Juan. For three or four miles above the mouth of the River Frio the lands are low and swampy. Several of its branches can be reached and navigated by canoe, and even a small river steamer can ascend a few miles from the lake. The San Carlos River joins the San Juan sixty-five miles from Lake Nicaragua. The depth of its mouth, which is obstructed by a sand-bar, varies from eight to twenty feet, according to the season. The San Carlos has numerous affluents which at times have a volume of water altogether disproportionate to their lengths. The distance up to the first rapid of the San Carlos River, which is at El Muelle de San Rafael where there are from four to six feet of water is roughly fixed at sixty-two miles by the course of the river. Small steamers could reach this point, although with difficulty on account of many snags. The floods sometimes rise to their full height in twenty-four hours and carry with them a great number of trees and much sand, from which floating islands are formed. Should the plans of Engineer Menocal for the Nicaragua Canal be realized, the waters of the upper San Juan and the lower San Carlos would be impounded and form an arm of Lake Nicaragua, which would flood a large area in Costa Rica. The interval between the San Carlos and the River Frio is an extensive forest, covering an undulating plain with occasional low hills and watered by numerous little streams. This territory is fertile and beautiful.