Captain McCallum moved up the river road to White's Ford or Noland's Ferry, where he crossed the Potomac and pushed for Leesburg; when within half a mile of that place, near the old fair ground, he encountered the pickets of the rebels; driving them a short distance, he brought in sigh about 450 rebel cavalry in line; he then fell back, moving slowly to the rear, followed by about 40 rebels in the road and by a squadron moving on his left through the fields, apparently for the purpose of cutting him off. As soon as the nature of the ground would permit he moved rapidly, and was then pursued more vigorously by the detachment in his rear. They continued to pursue him until he came within about a mile of the river at Monocacy; he crossed at that point by swimming his horses.

The rebel cavalry at Leesburg were reported to be a portion of Imboden's forces. A gentleman who escaped from Virginia yesterday reports that he was served with a notice to report, under the rebel conscript act, to Major White, and that Imboden's force were in Loudon for the purpose of enforcing the rebel conscript law.

Along the west bank of the river from Seneca to White's Ford there appeared to be parties engaged in reconnoitering the east shore.

Respectfully,

JAMES B. SWAIN,

Colonel.

Major J. P. SHERBURNE,

Assistant Adjutant-General.

SEPTEMBER 1-3, 1863.- Expedition Against and Destruction of Gunboats Satellite and Reliance at Port Conway, Va.

REPORTS.

Numbers 1.- Brigadier General Judson Kilpatrick, U. S. Army, commanding Third Cavalry Division, including skirmish (September 1) at Lamb's Creek Church.

Numbers 2.- Colonel Edward B. Sawyer, First Vermont Cavalry.

Numbers 1. Reports of Brigadier General Judson Kilpatrick, U. S. Army, commanding Third Cavalry Division, including affair September 1, near Lamb's Creek Church.

HEADQUARTERS THIRD CAVALRY DIVISION,
September 1, 1863-3 p. m.

GENERAL: My advance drove in the rebel pickets one-half mile north of King George Court-House. I am advancing on the three roads. I have not yet learned the strength of the enemy. The gunboats came up to Port Conway on Saturday.

Very respectfully,

J. KILPATRICK,

Brigadier-General.

General PLEASONTON.