Manual for submarine mining

EDITION OF 1912
WASHINGTON GOVERNMENT PRINTING OFFICE 1912
War Department, Document No. 399. Office of the Chief of Staff.
This Manual for Submarine Mining, revised to 1912, is approved and published for the confidential information and guidance of the Army of the United States. Under no circumstances shall its contents be divulged to persons not in the military or naval service of the United States.
By order of the Secretary of War:
Wm. H. Carter,
Major General, Acting Chief of Staff .
A submarine mine consists of an explosive charge inclosed in a water-tight case, and a firing device, the whole intended to be submerged in a waterway which it is desired to close against the passage of an enemy’s vessels.
With respect to the position of the case containing the explosive, submarine mines are of two classes, buoyant and ground.
In the buoyant mine, the case contains the explosive and the firing device, and has such excess of buoyancy that it would float were it not held below the surface by a mooring rope and an anchor. The submergence is such that, while the mine would be struck by the hull of a passing vessel, it is not so near the surface as to be seen.
Buoyant mines may be planted and operated successfully in water 150 feet deep. They should not, in general, be used where the depth of water is less than 20 feet.
In the ground mine, the case contains the explosive and the firing device, and is heavier than the displaced water; it therefore rests upon the bottom and requires no anchor. Ground mines are not used where the depth of water exceeds 35 feet.