Torpedoes.
We have seen an ingenious contrivance, by a gentleman of this city, which can be constructed at a trifling expense, that deserves the examination of the authorities in the defence of James river. One of these machines can be built at a cost of fifty dollars, and a dozen of them, placed in one of the channels, would send a Yankee fleet in five minutes to Davy Jones's locker. It is important that we should multiply obstructions to the passage of the enemy's gunboats, and any plan that is suggested by a responsible source deserves at least investigation.