CONFIDENTIAL.] HDQRS. CHIEF ENGINEER OF DEFENSES,

Washington, June 25, 1863.

Major General S. P. HEINTZELMAN,

Comdg. Department of Washington:

GENERAL: Our conversation this morning prompts the following remarks and suggestions: It was never supposed that the forts alone would protect Washington. Aided by darkness or fog, bodies of cavalry may pass between them, or columns of infantry may, if [aided] by artillery and infantry attacks upon the works themselves, the latter being fully employed otherwise, contrive to pass through. Nay, further, the works themselves are not deemed secure without full garrisons-i. e., the requisite infantry supports to man the parapets. I understand that not only are there no troops left to man the rifle pits and to support the artillerymen of the forts, but that even the number of artillerymen is not up to the standard. The safety of Washington is, therefore, dependent upon Hooker's army, and that army must constantly keep itself between the enemy, and every considerable body of the enemy, and the city. But Hooker ought to and doubtless will maneuver his army without such a trammel, and if he gives battle, whether in Virginia, Maryland, or Pennsylvania, he ought to give it with his whole force. A considerable body of cavalry might, under such circumstances, dash into and destroy Washington. In the absence of troops, we should have an organization of the citizens of Washington. I would suggest that some of the prominent citizens be invited and requested to make such an organization. It might not be expedient for the President, Secretary of War, or General-in-Chief to take any action in this matter, but the general commanding the department and intrusted with, the defense of the city might properly do it, and that without causing an unnecessary panic. The proceeding should be treated and regarded as purely precautionary, and founded simply upon the fact that Washington should never be without a garrison. In the report of the commission ordered by the Secretary of War on the Defenses of Washington, it was stated that a force of infantry of 25, 000 men and cavalry of 3, 000 should always be kept (independently of artillerymen) for the holding of Washington; and, morever, that-

Whenever an enemy is within striking distance of the capital-able by a rapid march to attempt a coup de main which might result in the temporary occupation of the city, the dispersion of the Government, and the destruction of the archives, all of which might be accomplished by a single day's possession-a covering army of not less than 25, 000 men should be held in position ready to march to meet the attacking column. The enemy is now within "striking distance, " and should the fluctuations of the campaign carry our own army from between him and the city, he might "be able by a rapid march" of all or a part of his army, "to attempt a coup de main, " &c. The Quartermaster's Department has a large number of employees, who, I am told, have been organized. The citizens and transient persons in Washington should be able to organize a force of 12, 000 or 15, 000 more. Altogether we might make up 15, 000 or 20, 000 men,