with General McClellan, I repaired to Boonsborough and returned via Frederick City to Baltimore. At Monocacy I found about 200 loaded cars on the sidings, some of which had been standing nearly a week. General Wool, at my request, sent an efficient officer of his staff to insist upon the unloading and return of cars. On Monday, September 22, I returned to Washington and made a verbal report to you of my doings. On Tuesday, September 23, having received information that the Baltimore and Ohio Railroad Company were embarrassed in their operation in consequence of the non-return of cars, I sent two of our most experienced train dispatchers from the Camden and Amboy Railroad over the Northern Central, Pennsylvania, and connecting roads to search for and return cars of Baltimore and Ohio Railroad Company, and of the U. S. military railroads. The same evening I started for Baltimore and Harper's Ferry to render such assistance as might be in my power in opening communications with that post. I arrived at Harper's Ferry about noon on Wednesday, September 24, and remained until Thursday afternoon, September 25. The supply of material being insufficient, and the force of mechanics for the railroad bridge very small, I telegraphed for the construction corps of the Camden and Amboy Railroad, which was promptly forwarded, together with about 150,000 feet of long, square timber, which we fortunately had on hand at Alexandria, and which could not elsewhere have been procured in time.

About six days will complete the railroad trestle bridge and secure connection by rail with Harper's Ferry, but a much longer time will be required to replace the permanent structure. The trestle bridge will be in danger of destruction from freshets. The most certain reliance for the supplies in the event of such a contingency will be the pontoon bridge which has been reconstructed. With proper management at Harper's Ferry and Sandy Hook, the supply question presents no difficulty, even in the case the trestle bridge should be swept away. These are: First. Sending supplies to the advanced terminus before they are required. Such supplies are not unloaded. They block the track, impede retreat, and are in danger of capture or destruction. Nothing should be sent to the extreme front until it is actually needed. A reasonable amount can be kept on some siding a few miles in the rear. Second. A second difficulty arises from the fact that cars are not promptly unloaded and returned. Sometimes only a single car will be unloaded at a time, when there should be force sufficient to discharge the contentsn. Cars are often kept for weeks as store-houses. Third. A third difficulry arises from the practice of detaining trains beyond schedule time. Nothing more certainly throws the business of a line into confusion, especially if there be but a single track. Medical directors and officers should conform to the schedule time of trains, or if extras are required for sick, wounded, or for supplies, they should always be furnished when practicable, but when the hour fixed for starting has arrived the trains should be promptly dispatched. It has been the practice on most roads used for military purposes, under the influence of a prssure of business and the impatience of military officers, to abandon the schedule and resort to the use of the telegraph exclusively for running trains. This practice invariably leads to difficulty and in case of any derangement to the delicate mechanism of the telegraph, puts an end to all business and blocks every wheel upon the road. I believe that it is always possible, with good management,