—In the French Chamber of Depu-ties, a short time since, M. Guizot, in answer to some ob-servations throwing doubts upon the practicability of the pro-posed works for piercing the Isthmus of Panama, read thefollowing letter from the Baron de Humboldt to one of theheads of the parties interested in the proposed operation.“I learn, with regret, that you are not further advanced inyour important enterprise than you were when I had last thepleasure of seeing you in Paris. For the last twenty-fiveyears, the project of a communication between the two seas,either by the Isthmus of Panama, by Lake Nicaragua, or bythe Isthmus of Capica, has been proposed, and topographically debated;and yet no beginning has been made. I shouldhave thought that the British Embassy would have found ameans of inspiring confidence in the proposal to send a scien-tific man (an engineer) for the purpose of examining thevalley which seperates the two seas, through which the canalmight be dug to the western side of the Port of Chagres. Beassured that those persons who use the authority of my namein support of the opinion that the two seas have differentlevels, do so only to excuse themselves from engaging in theenterprise.” The Minister also read an extract from a docu-ment addressed to the Academy of Sciences, by M. Warden,a distinguished American citizen, long consul for that countryin Paris:—“The cutting necessary to unite the two seas, bymeans of the three rivers, Vino-Tinto, Bernardino, and Farren,is but twelve and a half miles in length. The fall will beregulated by four double locks of 45 mètres long. The canalwill be altogether 49 miles in extent, 43 mètres 50 centimètreswide at the surface, 17 mètres 50 centimètres at the bottom,and having a depth of 6 mètres 50 centimètres. It will benavigable for vessels of from 1,000 to 1,400 tons burthen. Therivers, in those portions of them where they have from 2½ to4½ mètres of water, will serve for the canal, by deepening to6½ mètres; and the water will be maintained at that heightby two guard-locks. All the materials necessary for the con-struction of the canal are found on the soil which it has totraverse; and the total cost has been estimated at 2,778,615dollars, including the price of four steam-boats, and two ironbridges, 46 mètres long, and opening for the passage of ships.”