the inclosure and with an elevation of 40 feet above low-water mark, from which the prison, prison hospital, garrison, and post hospital may be supplied by means of hydrants place in convenient locations. The elevation of the reservoir will give a sufficient head of water to throw a stream over any building in the camp in case of fire. A slightly elevated ridge runs east and west through the center of the camp, and dividing it into two equal portions for drainage. The southern portion it is proposed to drain by means of a sewer leading into the main one, by which the above-mentioned marsh is to be drained into a natural ravine running to the river on the south side of the island. The prison streets are to be graded and furnished with surface drains leading into the main sewer. In the north avenue it is proposed to build an open sewer of masonry, over which are to be built the sinks, allowing th soil to be carried off by a stream of water constantly flowing from the reservoir through the sewer. On either side the sewer are to be built the wash-houses, to be supplied with water and drained into the sewer which is to empty into the river below low-water mark, and to be efficiently protected from being used by the prisoners as a means of escape. A copy of this plan has already been sent to Washington, and will, I hope, meet your approval and that of the Quartermaster's Department, for it or some similar plan is most necessary. There is at present no prison hospital, prisoner barracks being now used for that purpose. I have approved a plan, a copy of which has been forwarded for your approval. I have carefully reconnoitered the island and selected a site about 500 feet south of the inclosure and west of the reservoir. The ground is elevated and can be readily drained into the marsh sewer and is sufficiently near the reservoir to receive a supply of water. Captain Reynolds, in anticipation of the authorization of the building by the Quartermaster's Department, has already begun the cleaning to the ground. The most urgent necessity exists for the speedy completion of this building. The smallpox hospital is located on the south shore of the island, directly opposite the prison, and at present consists of 3 barracks, each 129 by 22 by 12 feet in dimensions and accommodating 42 beds in each, and 3 small dwelling houses, unfit for any use at all, except for kitchens or wash-houses. Three additional barracks of the same dimensions as the above are in process of erection by my direction. there are now over 100 cases of smallpox within the prison inclosure, and it is of the utmost importance that they should be removed as rapidly as possible. I inclose an application* to the Surgeon-General for the assignment of a capable medical officer to the charge at Rock Island, which, if it meets your approbation, please approve and forward to the Surgeon-General's Office. I leave to-night for Springfield, Ill.

Very respectfully, your obedient servant,

A. M. CLARK,

Surgeon and Acting Medical Inspector of Prisoners of War.

OFFICE COMMISSARY-GENERAL OF PRISONERS,

Washington, D. C., February 13, 1864.

Brigadier General G. MARSTON,

Commanding Depot Prisoners of War, Point Lookout, Md.:

GENERAL: On yesterday, by direction of the Secretary of War, I addressed a telegram to Major-General Butler, commissioner for exchange,

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*Omitted.

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