Taking Observations of our forces.
Washington, Aug. 24.
--Observances taken from the Alexandria and Loudoun Railway show that the Confederate camps at Leesburg contain 3,000 infantry and six cannon; at a point six miles below there are 6,000 men with six cannon; four miles beyond there are 3,500 men; also that there are 2,000 cavalry in Loudoun county.
The Potomac remains too high to be forded even by the cavalry.