Thomas T. Gantt, aide-de-camp, until compelled by ill-health to retire, at Harrison's Landing, in August, 1862. His reviews of the decisions of courts-martial during this period were of great utility in correcting the practice in military courts, diffusing true notions of discipline and subordination, and setting before the army a high standard of soldierly honor. Upon the retirement of Colonel Gantt the duties of judge-advocate were ably performed by Colonel Thomas M. Key, aide-de-camp.

SIGNAL CORPS.

The method of conveying intelligence and orders, invented and introduced into the service by Major Albert J. Myer, Signal Officer, U. S. Army, was first practically tested in large operations during the organization of the Army of the Potomac.

Under the direction of Major Myer a Signal Corps was formed by detailing officers and men from the different regiments of volunteers and instructing them in the use of the flags by day and torches by night.

The Chief Signal Officer was indefatigable in his exertions to render his corps effective, and it soon became available for service in every division of the army. In addition to the flags and torches, Major Myer introduced a portable insulated telegraph wire, which could be readily laid from point to point, and which could be used under the same general system. In front of Washington, and on the Lower Potomac, at any point within our lines not reached by the military telegraph, the great usefulness of this system of signals was made manifest. But it was not until after the arrival of the army upon the Peninsula, and during the siege and battles of that and the Maryland campaigns, that the great benefits to be derived from it on the field and under fire were fully appreciated.

There was scarcely any action or skirmish in which the Signal Corps did not render important services. Often under heavy fire of artillery, and not infrequently while exposed to musketry the officers and men of this corps gave information of the movements of the enemy and transmitted directions for the evolutions of our own troops. The report of the Chief Signal Officer, with accompanying documents, will give the details of the services of this corps, and call attention to those members of it who were particularly distinguished.

TELEGRAPHIC.

The telegraphic operations of the Army of the Potomac were superintended by Major Thomas T. Eckert, and under the immediate direction of Mr.

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Caldwell, who was, with a corps of operators, attached to my headquarters during the entire campaigns upon the Peninsula and in Maryland. The services of this corps were arduous and efficient. Under the admirable arrangements of Major Eckert they were constantly provided with all the material for constructing new lines, which were rapidly established whenever the army changed position, and it was not infrequently the case that the operatives worked under fire from the enemy's guns, yet they invariably performed all the duties required of them with great alacrity and cheerfulness, and it was seldom that I was without the means of direct telegraphic communication with the War Department and with the corps commanders. From the organization of the Army of the Potomac up to November 1, 1862, including the Peninsular and Maryland campaigns, upwards of 1,200 miles of military telegraph line had been constructed in connection with the operations