A gentleman in DeKalb county, Indiana, writes to us that he is ready to serve Uncle Abe by entering the gunboat service, and inquires for the rendezvous. We have had several letters of the same import. In reply, we say that Cairo is the place. If our friends want to serve their country in earnest, let them call at once upon Commodore Foote, at Cairo. They will find him a most estimable man—a gentleman, in every sense of the the term, a son of old Connecticut, who is a stranger to fear, who believes in fighting, who has been under hot fire several times in his life, who is also cool, deliberate, judicious, earnest; whose whole soul is in this war, and who will, provided he can get ordnance and men, force the rebels to make quicker time from Columbus than the chivalric South Carolinians made from Tybee.