Of course the deepest throb of interest is given to the work at the front of battle. That is natural. It is work done on the very spots where the fortunes of our nation are being decided,--on the spots whither all eyes are turned, and towards which all our hopes and prayers go forth. It is work surrounded by every element of pathos and tragic interest. The wavering fortunes of the fight, the heroic courage which sustains a doubtful conflict, the masterly skill that turns disaster into triumph, the awful carnage, the terrible suffering, the manly patience of the wounded, all combine to fix the attention there and upon everything, which is transacted there. The question is constantly asked,--What is the Sanitary doing at the front? what at City Point? what at Winchester? are natural questions. Let me state first the general plan and method of what I may call a Sanitary campaign, and afterwards add what I saw with my own eyes at City Point and before Petersburg, and what I heard from those who had themselves been actors in the scenes which they described. When the army moves out from its encampment to the field of active warfare, two or three Sanitary wagons, loaded with hospital stores of all sorts, and accompanied by a sufficient number of relief agents, move with each army corps. These are for the supply of present need, and for use during the march, or after such skirmishes and fights as may occur before the Commission can establish a new base. In this way some of the Commission agents have followed General Grant's army all the way from the Rapidan, through the Wilderness, across the Mattapony, over the James, on to the very last advance towards the Southside Railroad,--refilling their wagons with stores as opportunity has occurred. As soon now as the march commences and the campaign opens, preparations upon an extensive scale are made at Washington for the great probable demand. Steamers are chartered, loaded, and sent with a large force of relief agents to the vicinity of the probable battle-fields; or if the campaign is away from water communication, loaded wagons are held in readiness. The moment the locality of the struggle is determined, then, under the orders of the Provost Marshal, an empty house is seized and made the Sanitary head-quarters or general storehouse; or else some canal-barge is moored at the crazy Virginia wharf, and used for the same purpose. This storehouse is kept constantly full from Washington, or else from Baltimore and New York; and the branch depots which are now established in each army corps are fed from it, while the hospitals in their turn make requisitions for all needful supplies on these branch depots. That is to say, the arrangements, though rougher and less permanent in their character, approximate very nearly to the arrangements at Washington.