The Spanish discoverers of the great Lake Nicaragua, coming upon it from the Pacific, and noting the fluctuations of level caused by the action of the wind upon its broad surface, mistook these fluctuations for tides and felt assured that some broad strait connected it with the North Sea. Later, when Machuca had discovered the grand river outlet of the lake, and the restless searching of other explorers in every bay and inlet along both sides of the American isthmus had extinguished forever the ignis fatuus "Secret of the Strait," Gomara pointed this out as one of the most favorable localities for an artificial communication between the North and South Seas. [Illustration: THE NICARAGUA CANAL. _Julius Bien & Co._] It was not until 1851, however, that an accurate and scientific survey of a ship canal route was made by Col. O. W. Childs. This survey which showed the lake of Nicaragua to be only one hundred and seven feet above the sea, and the maximum elevation between the lake and the Pacific to be only forty-one feet, exhibited the advantages of this route so clearly and in such an unanswerable manner that it has never since been possible to ignore it. In 1870, under the administration of General Grant and largely through the unceasing efforts of Admiral Ammen, the United States began a series of systematic surveys of all the routes across the American isthmus from Tehuantepec to the head waters of the Rio Atrato; and six years later, with the plans and results of all these surveys before it, a commission composed of General Humphreys, Chief of Engineers, U. S. Army; Hon. Carlile Patterson, Superintendent U. S. Coast Survey; and Rear-Admiral Daniel Ammen, Chief of Bureau of Navigation, U. S. Navy; gave its verdict in favor of the Nicaragua route. The International Canal Congress at Paris, in 1879, had such convincing information placed before it that it was forced, in spite of its prejudices, to admit that in the advantages it offered for the construction of a lock canal, the Nicaragua route was superior to any other across the American isthmus. In 1876, and again in 1880 Civil Engineer A. G. Menocal, U. S. N., the chief engineer of previous governmental surveys, resurveyed and revised portions of the route, and in 1885 the same engineer, assisted by myself, surveyed an entirely new line on the Caribbean side, from Greytown to the San Juan river, near the mouth of the San Carlos. On the eastern side of Nicaragua, all these surveys (except the last), were confined almost entirely to the San Juan river, and its immediate banks; and the country on either side beyond these narrow limits was, up to 1885, almost entirely unknown. Between Lake Nicaragua and the Pacific, however, every pass from the Bay of Salinas to the Gulf of Fonseca had been examined.