completed and are ready for occupation, though there is yet some unfinished work. In consequence of the extent of the inclosure and the less efficient character of the Invalid Corps than other troops the accommodations for the guard will have to be more extensive than was anticipated, and some little time will elapse the additions which are in progress will be completed. This, however, will not delay the reception of prisoners. I found but four companies present, two of which had just arrived, and as no medical officer had been appointed I applied to assistant surgeon-general in Louisville for one to be ordered there, with a supply of medicines and stores. My request was immediately complied with, and I have since asked that other medical officers may be ordered there. Since my return to this city the guard has been increased to a regiment and the depot is placed under the command of Colonel R. H. Rush, of the Invalid Corps, who, I feel confident, will soon have it so organized and administered as to give the most satisfactory results.

With the exception of a small part of it Rock Island belongs to the United States, and it is very desirable that it should be placed under martial law, in order that the commanding officer may have it in his power to prevent the instruction of persons who will take advantage of every opportunity to enter into an illicit traffic with the guard or the prisoners. The Chicago and Rock Island Railroad crosses the island and should not be allowed, without the permission of the commanding officer, to land passengers on the island.

On Tuesday evening I left Rock Island for Sandusky, where I arrived on Thursday morning and proceeded at once to the depot on Johnson's Island, where I met General Cox, who had a considerable force with him drawn there by the threatened attempt from Canada to rescue the prisoners. I met there also Captain Carter, or Navy, the commander of the U. S. steamer Michigan, which was lying off the island.

At the Michigan had been lying in Sandusky Bay at the request of the War Department some ten days when the report of the threatened invasion was made there was no possible chance of its being attended with any success, even if the rebels could have been sufficiently secret in their preparation to have left a Canada port without detection, but that, as the results show, was not possible.

Some threats, it is reported, have been made by the prisoners on the island to take advantage of some opportune moment to overcome the guard and make their escape to Canada, but their situation must be much more desperate toe they will attempt, with naked hands, to attack a vigilant guard armed with muskets and revolvers, when success, which is only within the reach of possibility after great sacrifices, would only place them on an island from which they could no escape.

General Cox will withdraw all his troops except five companies of cavalry recruits, who will remain on the island until relieved by some of the companies ordered to be added to the battalion to make it up to a regiment. I doubt if quarters for more than two companies can be built this season, and with this increase of the strength of the guard I think the prisoners will be perfectly secure for the winter.

In consequence of the dangers which it has been represented would attend her wintering in Sandusky Bay the Michigan has been ordered to return to Erie before the navigation of the lake closes.

While General Orme, who accompanied me to the island, was inspecting the prisoners in pursuance of your instructions I examined the ground with a view to decide on the best location for the barracks about