Commencing at the mouth of the Atrato River, the work to be done is described as follows: The mouth of the Atrato being obstructed by bars, the caño coquito, by which the river is to be united with the Gulf of Urabà, having at the present time a depth of four feet water, is to be excavated to a depth of thirty feet. From thence sixty-five miles to the mouth of the Truando, the depth is not less than forty-seven feet. The bar at the mouth of the Truando is eighteen feet. For six miles the river has an average depth of fourteen feet. From thence to the Pacific, twenty-six miles, much of the distance is through solid rock. At 505 feet above the ocean level, Mr. Kennish proposes to pierce the divide by a tunnel three and one-half miles in length, sufficiently large to admit two ships abreast. The harbor at the Pacific terminus requires improvement; guard locks not considered necessary. Total length of the line, one hundred and twenty-six miles. The results of this survey were regarded as highly favorable by the friends of the measure. Mr. Kelley regarded his labors and expenditures as well rewarded. “Franklin,” he observes, “was not more delighted when he drew lightning from the clouds, nor Columbus when he discovered America, than I was when it was demonstrated, by instrumental measurement, that the two oceans could be united, that all the science, industry, enlightened enterprise, and generous expenditure had not been exhausted in vain.” To verify this survey, Congress authorized the Secretaries of War and Navy to organize a joint expedition. In accordance with this authority, the Secretary of the Navy designated Com. Craven. This gallant officer was afterward sunk off Mobile, and lost with all the crew of his ship. MICHLER’S ROUTE. To Lieut. N. Michler, Corps of Topographical Engineers, (now Brevet Brigadier-General,) the execution of the topographical survey was assigned. The operations of this officer were published in the form of a diary, with special scientific reports and observations, accompanied by maps and profiles. The special reports embrace observations upon geology, botany, hipsometrical and astronomical determinations, climatology, and field notes. The itinerary is full and interesting, supplying information valuable to future explorers. The reader is never asked to accept a statement upon the _ipse dixit_ of the writer. The observation of a corps of intelligent surveyors is laid before the reader.