Sir,

It has so happened, that your favor of the 19^th. Ulto. did not come to my hands until the last mail arrived at Alexandria. By the return of which, I have the honor to address this letter to you.

Mr. McMeiken’s explanation of the movements of Rumsey’s* newly invented Boat, is consonant to my ideas; and warranted by the principles upon which it acts. The small manual assistance to which I alluded, was to be applied in still water; and to the purpose of steering the vessel. The counteraction being proportioned to the action, it must ascend a swift currt. faster than a gentle stream; and both, with more ease than it can move on dead water. But in the first there may be, and no doubt is, a point beyond wch. it cannot proceed without involving consequences which may be found insurmountable. Further than this I am not at liberty to explain myself; but if a model, or thing in miniature can justly represent a greater object in its operation, there is no doubt of the utility of the invention. A view of this model, with an explanation, removed the principal doubt I ever had in my mind, of the practicability of progressing against stream, by the aid of mechanical Power; but as he wanted to avail himself of my introduction of it to the public attention, I chose, previously, to see the actual performance of the model in a descending stream, before I passed my certificate, and having done so, all my doubts were done away.