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

We now come to a more useful device of the purely defensive type
employed to screen surface ships from submarine attack. The very simple
mechanical and chemical apparatus needed for making the heavy clouds of
smoke needs no description beyond that given in the text, but something
must be said here regarding the methods of use.

It was not until the third year of the Great War had been ushered in by
the unprecedented sinking of Allied merchantmen by German U-boats that
the value of the smoke screen as a means of baffling an under-water
attack was fully realised. Convoy guards were supplied with the
necessary appliances for emitting the fumes with which to cover the
movements of the ships under their protection, and so successful was
this method of blinding attacking submarines that within a few months
thousands of transports, food-ships and warships had been equipped.

When a submarine proclaimed her presence in the vicinity of a convoy
either by showing too much of her periscope or by a misdirected torpedo,
the guard-ships on the flank attacked immediately dropped their smoke
buoys as they continued moving at full speed. By this means an
impenetrable optical barrier was interposed between the attacking
submarine and the fleet of merchantmen under convoy. When thus shielded
from attack--a submarine values her small stock of torpedoes (six to
ten) too highly to risk the loss of one or more on something she cannot
even see--the mercantile fleet altered course so as to present their
sterns to the attacking U-