This elaborate and costly anti-submarine device was very widely, but not altogether successfully, employed by the auxiliary fleet during the first two years of war. It was nothing more than a long explosive tail towed submerged by a surface ship, the object being to either drag it over a submarine resting on the sea-bed, or else, if the under-water craft was moving, to so manoeuvre the towing surface ship as to swing the tail close to the U-boat, when the heavy charges of T.N.T. attached to the armoured electric cable, forming the tail, would be exploded either by actual contact with the hull of the enemy, or, when sufficiently close to be effective, by the closing of a firing circuit on board the surface ship. [Illustration: FIG. 13.--Diagram showing a vessel towing a modified sweep. This appliance consists of an armoured electric cable _G_ towed in vertical loop under the surface. The floats _D_ support the 100-lb. charges _E_, which have strikers attached. If a submarine _B_ is lying "doggo" on the sea-bed one or other of these charges may strike her hull and the whole line then blows up, shattering everything in the surrounding sea. If the strikers fitted on the charges do not touch the submarine the whole line can be exploded at will from the surface ship by closing an electric circuit.] Excellent in theory but very difficult of accomplishment in actual practice. The diagram given will explain the details of this elaborate contrivance, which, however, was soon discarded for more practical methods, although at least one German submarine is known to have been destroyed by it. LANCE BOMBS These little engines of destruction were intended for fighting at close quarters, and can be described here in a few lines because of their guileless simplicity. They consisted of conical explosive bombs on the ends of broom handles! A strong man could whirl one of them round his head, like a two-handed sword or battle-axe, and, when the momentum was sufficient, hurl it over the water for about seventy-five feet. On nose-diving into the sea and hitting the hull of a submarine in the act of rising or plunging, the little bomb, containing about 7 lb. of amatol, was exploded by contact. [Illustration: FIG. 14.--A lance bomb. The wooden handle _A_ enables the charge _B_ (7 lb. of high explosive) to be whirled round the head and hurled a distance of about twenty yards.] The damage inflicted on one of the earlier types of submarines by an under-water hand-grenade or lance bomb depended entirely upon what part of the vessel happened to be struck. Their sphere of usefulness was, from the first, very limited, and the advent of the big cruiser submarine, with armoured conning-tower and 5-inch guns, rendered them obsolete. SMOKE SCREENS