The subjoined interesting letter is from Alexander vonHumboldt on the subject of the projected oceanic canalacross the Isthmus of Darien. The importance of theundertaking is fully admitted by the learned baron;and he urges the necessity of constructing a canalwithout locks as the only medium of communicationsuitable for the accommodation of the trade of theworld. It is now said that it was to the absence of thisimportant feature in the Nicaragua ship-canal-schemethat the failure of that project was mainly owing:—

“After having laboured in vain, during half a century,to prove the possibility of an oceanic canal, and topoint out the Gulf of San Miguel and Cupica as thepoints most worthy of attention—after having regretted,almost with bitterness, in the last edition of my‘Aspects of Nature,’ that the employment of the meanswhich the present state of our knowledge affords forobtaining precise measurements has been so longdelayed, I ought, more than any one else, to be satisfiedto see, at last, my hopes for so noble an enterpriserevived. By your publications, and by that of Mr.Gisborne, will be originated the great work of changingan important part of the commerce of nations, and ofrendering more accessible the rich countries of EasternAsia and the Indian Archipelago. The undertaking isby no means above the intellectual and material powerwhich civilised nations have attained to. The workshould be one to last for ever—it should not commencewith a canal with locks like the magnificent CaledonianCanal—it must be a really oceanic canal without locks—a free passage from sea to sea, across which the speedof the navigation will be modified, but not interrupted,by the difference in height and non-coincidence of thetides.