...uns, and sent up a transport with the pretext, it was said, of effecting an exchange of prisoners. But at that time, as we learned afterward from a credible source, the evacuation of the fort (which General Grant 's successes at Forts Henry and Donelson had made necessary) was going on, and the last raft and barge loads of all the movable munitions of war were descending the river, which, with a large quan...