FALMOUTH, VA., opposite Fredericksburgh, December 21, 1862.—Begin my visits among the camp hospitals in the army of the Potomac. Spend a good part of the day in a large brick mansion on the banks of the Rappahannock, used as a hospital since the battle—seems to have receiv'd only the worst cases. Out doors, at the foot of a tree, within ten yards of the front of the house, I notice a heap of amputated feet, legs, arms, hands, &c., a full load for a one-horse cart. Several dead bodies lie near, each cover'd with its brown woolen blanket. In the door-yard, towards the river, are fresh graves, mostly of officers, their names on pieces of arrel-staves or broken boards, stuck in the dirt. (Most of these bodies were subsequently taken up and transported north to their friends.) The large mansion is quite crowded upstairs and down, everything impromptu, no system, all bad enough, but I have no doubt the best that can be done; all the wounds pretty bad, some frightful, the men in their old clothes, unclean and bloody. Some of the wounded are rebel soldiers and officers, prisoners. One, a Mississippian, a captain, hit badly in leg, I talk'd with some time; he ask'd me for papers, which I gave him. (I saw him three months afterward in Washington, with his leg amputated, doing well.) I went through the rooms, downstairs and up. Some of the men were dying. I had nothing to give at that visit, but wrote a few letters to folks home, mothers, &c. Also talk'd to three or four, who seem'd most susceptible to it, and needing it.