EXECUTIVE MANSION.

Washington, July 13, 1862

Major-General McCLELLAN:

MY DEAR SIR: I am told that over 160,000 men have gone into your army on the Peninsula. When I was with you the other day we made out 86,500 remaining, leaving 73,500 to be accounted for. I believe 23,500 will cover all the killed, wounded, and missing in all your battles and skirmishers, leaving 50,000 who have left otherwise. Not more than 5,000 of these have died, leaving 45,000 of your army still alive and not with it. I believe half or two-thirds of them are fit for duty to-day. Have you any more perfect knowledge of this than I have? If I am right, and you had these men with you, you could go into Richmond in the next three days. How can they be got to you, and how can they be prevented from getting away in such numbers for the future?

A. LINCOLN.

HEADQUARTERS FIRST CAVALRY BRIGADE.

Westover, July 13, 1862

Captain A. J. ALEXANDER,
Acting Assistant Adjutant-General:

SIR: I have the honor to report that yesterday morning Lieutenant-Colonel Owen went with three squadrons of cavalry toward Long Bridge for the purpose of ascertaining if the enemy had crossed the Chickahominy at that point.

He met the enemy in considerable force at Saint Mary's Church, 8 miles beyond our pickets,on the Long Bridge road. He attacked and drove these pickets back to their infantry support, but could push them no farther.

Captain White, Third, Pennsylvania Cavalry was sent to cross the Chickahominy at Jones' Bridge and communicate with the pickets of Colonel Campbell in New Kent County.

A squadron of the Fourth Pennsylvania was sent last night to Charles City Court-House to occupy and hold the road leading from that point to Long Bridge in order to cover the movements of Captain White. In the operations of yesterday there was some skirmishing at Saint Mary's Church in which some of the enemy were believed to have been killed and wounded. Three prisoners were taken; two of them were sent to the provost-marshal-general, but the men who were bringing him to me by Brigadier General W. F. Smith. An ignorant contraband on his way to Richmond from New Kent was also taken and sent up.

Later.- I have just received a dispatch from Captain White at Jones' Ford: "No trace of the enemy there now; no troops at Providence (Barton's) Ford since Thursday."

I shall hear from him again to-night. As soon I have the maps corrected for the country in direction of Long Bridge I will send up a sketch.

Four companies Fifth U. S. Cavalry are out with Brigadier-General Barnard, engineer, on the Charles City road.

There are all together fourteen companies out from this brigade at the present time, as follows, viz: Eight on Long Bridge road, two over