Major-General Foster, with the iron-clad Sangamon and the gunboats Commodore Barney, General Jessup, and Cohasset made an expedition up the James River. At a point seven miles from Fort Darling, near Dutch Gap, a torpedo was exploded under the bows of the Commodore Barney, by a lock-string connected with the shore. The explosion was terrific. It lifted the gunboat's bows full ten feet out of the water, and threw a great quantity of water high into the air, which, falling on the deck, washed overboard fifteen of the crew. Among them was Lieutenant Cushing, the Commander of the Commodore Barney. Two sailors were drowned. All the rest were saved. Major-General Foster was on board the boat when the explosion took place. The rebels then opened upon them from the shore with a twelve-pound field-piece. The Barney was penetratedt by fifteen shots, beside a great number of musket-balls; but not a man was injured except the paymaster, who was slightly wounded by splinters. The gunboat Cohasset received five twelve-pound shots, one of which passed through her pilot-house and instantly killed her Commander, Acting Master Cox, striking him in the back.--A brisk skirmish took place near Brandy Station, Va., between a party of National troops under the command of General Merritt and Colonel Davis, and a large number of rebels, resulting in the retreat of the latter, with a loss of two killed and one wounded. The National loss was one killed and two wounded.