Chicago, April 1—A special dispatch to the Journal from Cairo says that Col. Buford yesterday, accompanied by the 27th and 47th Illinois Regiments, and part of the 15th Wisconsin Regiment, from the force near Island No. 10, with a detachment of cavalry and artillery from Hickman, under Col. Hedge, made a descent upon Union City, Tenn, after a forced march of 30 miles, and fell on the rebel encampment there at 7 o’clock In the morning, dispersing the entire force stationed there under Clay King, both cavalry and infantry.