It is fresh in your memory how Pope's campaign resulted. Disorganized trains and wearied and dispirited troops were crowded in on Washington and Alexandria during the latter days of August.

General McClellan was invested on the 4th of September with the command of the "defenses of Washington." At the same time I ordered all quartermasters to draw supplies, to place their commands in marching condition, and to reorganize their trains at once.

These orders were obeyed very promptly. There was probably some 2,500 wagons conducted in by Colonel Fred. Myers to Alexandria, which he saved from the recent retreat if General Pope. These, added to what had arrived from the peninsula and what General Rusker could spare from the Washington depot, made up the train for the Maryland campaign.

It was soon ascertained that portions of the rebel army had crossed the Potomac, and had entered Maryland above Harper's Ferry. On the 5th and 6th of September our army was put in march toward Frederick City, by Rockville and Urbana.

I left Washington on the 7th instant, and joined headquarters same day at Rockville. We remained there two or three days, while our cavalry and advanced infantry and artillery commands were gaining information of the enemy and feeling of his position. Meantime General McClellan became possessed of the plans of the rebel general, and the army was pushed on through Frederick to the gorges of South Mountain, where the rebels made their first stand of any importance.

The battle of South Mountain was fought on the 13th and 14th of September. That victory opened the Cumberland Valley. The army followed rapidly, and came up with the entire rebel army in position on the heights of Sharpsburg on the 15th instant.

The battle of Antietam was fought on the 17th, and resulted in favor or our arms, freeing Maryland completely of the enemy, and compelling him to retreat into Virginia.

The army was supplied by our wagon trains exclusively, until we recaptured Frederick. The enemy had burned the railroad bridge over the Monocacy, but a depot was established on the left bank while the bridge was being rebuilt, and supplies of subsistence and forage were brought up over the Baltimore and Ohio Railroad; Captain J. C. Crane, assistant quartermaster, was placed in charge. The commands within reach sent wagons to this depot for what they required. Wagon trains were also kept plying between Washington and the army until after it had passed South Mountain. A depot was nest established at Hagerstown, under Captain George H. Weeks, assistant quartermaster, and supplies of clothing, subsistence, and forage were brought over the Cumberland Valley Railroad.

These supplies came mainly from Washington, but forage and clothing were frequently brought direct from New York City, Philadelphia, and Baltimore. After the battle of Antientam the army was assembled about Harper's Ferry. The canal was now available; with all these sources of transportation we had no embarrassment, save in the extreme slowness, in some instances, with which stores turned over to the railroad for transportation were delivered at their destinations. From this cause we were unfortunately very late in receiving clothing, and much of it arrived at Berlin too late for issue, as the army was already on its march to White Plains, Warrenton, &c.

Generally, however, the railroads did splendid service. I always found the principal officers and agents of the roads extremely obliging, courteous, and energetic.