Colonel G. W. Hughes, in a letter to the Hon. J. M. Clayton, at that time Secretary of State, makes the following observations in regard to this route: “The line I have traced for a railroad is, I think, more favorable for a ship canal than that suggested by M. Garella. If we adopt the same depth of cutting he suggests for an open cut, it will leave the bottom of the canal 44 feet above the level of the Pacific at high tide. This would be about ten feet lower than the bed of the river at Gorgona. An open cut two hundred feet deep would obviate all difficulty in crossing the Chagres at Gorgona, while the Rio Grande, the Obispo, and the Mandingo might be converted into an immense reservoir for supplying the summit-level with water, and the Rio Chagres above Cruces, and the Pedro, Miguel, Camero, etc., would furnish the lower level. A spacious tide basin might be constructed at the mouth of the Rio Grande, a few miles west of Panama.” For this project, so favorably recommended, it is necessary to obtain the consent of the Panama Railroad Company to the use of land belonging to their reservation. SAN BLAS AND BAYANO RIVER. This route is one of several surveyed under the generous patronage of F. W. Kelly and others. The map of Mr. McDougal, the surveyor and engineer, and the report of Admiral Davis, furnish some interesting facts. The narrowest part of the Isthmus is found here, being thirty miles from ocean to ocean, and here the tide of the Pacific is said to approach within fifteen miles of the Atlantic coast. Mr. McDougal proposes to pierce the ridge, which has an altitude of 1500 feet, at a height of 93½ feet above mean tide, by a tunnel seven miles long. The harbor of San Blas is deep and spacious. The channel leading into the Bay of Panama has not less than eighteen feet of water at mean low tide, while the rise of the water is sixteen feet. This result, Admiral Davis observes, does not agree with the admiralty charts. The map indicates the probable existence of a better route to the north-west, and the surveyors were satisfied they saw evidences of a depression in that direction. Admiral Davis quotes the well-merited compliment of Sir R. Murchison, to the zeal and energy with which Mr. Kelly has pursued “this great and philanthropic object,” in which “all civilized nations are deeply interested.” DARIEN. Between Caledonia Bay and the Gulf of San Miguel every effort to make a thorough exploration has resulted in failure. Disappointed expectations, arduous but fruitless labors, conflicting reports, failure, starvation, and death have stamped with ill omen every attempt to cross this part of the Isthmus. Baron Humboldt has directed public attention to Darien, and Admiral Davis expresses his deliberate conviction that to this part of the Isthmus we must look for a solution of the question of interoceanic ship communication.