When for want of rank, I was superseded in the command, I continued to discharge the duties of engineer, under the full conviction that in that crisis (September 1) I could render no more valuable service to my country than to perfect the defenses of Washington.

I commenced on my first arrival to strengthen this part of the line. I directed the enlargement of Fort Massachusetts, and laid out forts and batteries to make a complete connection between the first-named work and Fort Alexander on the Potomac; at the same time I felled the timber to a distance of a mile in front, thus exposing the ground and making it impracticable to the enemy's movements.

On the south of the Potomac rifle-pits were thrown up between the works, new gun-platforms laid, and the armament improved; obstructions made across the valleys of Four-Mile Run and Hunting Creek; Fort Lyon strengthened by advanced works, and batteries for field guns prepared. On the most prominent or commanding points 100-pounder rifled guns, on center pivot carriages, were introduced, to bring under fire the whole external area an enemy must occupy in approaching our lines. These, and similar works, are fully described in the report of the Commission.

With no other assistance from engineer officers than that of a single officer (valuable, indeed-that of Lieutenant Colonel B. S. Alexander), it has been necessary to employ a large number of civil assistants, superintendents, and oversees, to supervise the works and troops and laborers employed. This, together with the hire of laborers, the purchase of lumber and other materials, has required a large cash expenditure. You authorized (in August, I think) the application of $50,000 from the appropriation for the contingencies of fortifications, field works, &c.,; to the Defenses of Washington, $50,000 more. This last sum will have been nearly exhausted at the end of this month.

It is exceedingly difficult to estimate for this kind of expenditure, and as the exigencies of the service have, since my return here, made it impossible to furnish the number of troops required for the labor, I am obliged to suppose that much of the additional work proposed by the Commission will be done by hired labor, and, making reference to past results, to estimate that an additional sum of $200,000 will be needed; for which I ask that an appropriation of Congress be requested. I also request that, until such an appropriation be made, I may be authorized to apply an additional $50,000 from the existing appropriation for contingencies of fortifications.

There has been but one other system of field works that I know of that is analogous to this in extent and character-the famous lines of Torres Vedras. These frustrated the design of Napoleon of driving the English from the Peninsula. They consisted of a greater number of works, but the works were smaller, and much less expensive in work-manship; yet on these lines, in a country where labor commanded but one-tenth of what is paid in this country, $1,000,000 was expended from first to last.

I am, very respectfully, your most obedient,

J. G. BARNARD,

Brigadier General,and Chief Engineer Defenses of Washington.

[Inclosure.]

WASHINGTON, December 24, 1862

Honorable E. M. STANTON, Secretary of War:

SIR: The Commission appointed by Special Orders of the War Department, Numbers 312 dated Washington, October 25, 1862, "to examine