Lieut. Hunter Davidson, his valued assistant, succeeded him in charge of the James River batteries, and in time extended the mines some distance below. During the two years when he was in charge he planted many electrical torpedoes in the channel of the river, to be fired from concealed stations on shore. Some of these contained 1,800 pounds of powder. In August, 1862, the Federal steamer "Commodore Barney" was badly disabled by one of these, and in 1864 the "Comm. Jones" was totally destroyed, with nearly all on board, the first fruits of Maury's electrical torpedo defense. The first vessel destroyed by a submarine torpedo was the gunboat--ironclad--"Cairo," in the Yazoo River. The torpedo was a demijohn of powder enclosed in a box sunk in the river and fired by a string from the shore. Lieut. Beverley Kennon claimed the credit for this but Masters McDaniel and Ewing did the actual work. Early in 1864 Davidson, in a steam launch, specially constructed for him, called "The Torpedo," having made 120 mile run down James River, all within the enemies' lines, exploded a torpedo against the flagship "Minnesota," at anchor off Newport News. The river swarmed with the enemy's vessels, and the guard boat was lying by the "Minnesota," but her captain had allowed his steam to go down. Davidson hit the great ship full and fair, causing great consternation on board, but the torpedo charge was only fifty-three pounds of powder and it failed to break in her sides, although considerable damage was done. Davidson suffered no injury and returned to Richmond without incident. On August 9, 1864, there was a great explosion in Grant's lines at City Point, on the James, caused by a torpedo with a clock attached which caused it to explode at a given hour. With daring unexcelled John Maxwell and R. K. Dillard, of the torpedo corps, made their way into the lines, carrying the machine neatly boxed with them, which Maxwell handed aboard one of the boats lying at the wharf, saying that the captain had directed him to do so. In half an hour there was a terrible explosion, killing and wounding fifty men and destroying much property and many stores besides, injuring many nearby vessels, which brave John Maxwell quietly witnessed seated upon a log upon a hillside close by. Lieut. Beverly Kennon was also most active in this system of defense and personally planted many torpedoes in the Potomac, Rappahannock and the James. He and Lieut. J. Pembroke Jones succeeded Lieutenant Davidson in charge of the torpedo defense of the James. A defense in itself equivalent to a well appointed fleet or army, since, as is well known, it served to keep the enemy out of Richmond till the close of the war, and converted them into earnest advocates of its use.