Troops for Fort Delaware.
--A telegraphic dispatch was received at Fort Columbus, New York, at quarter past 4 P. M., on Tuesday, from Gen. Scott, ordering a detachment of 30 men for Fort Delaware, to leave forthwith.--At a quarter past five--one hour after the order was received --the detachment left the island under command of Lieut. Wood, each man armed with his rifle, and 25 rounds of ball cartridge. Pretty prompt work, that.