typical picture of guerrilla war at sea in the twentieth
century.

[Illustration: FIG. 5.--Diagram illustrating method of attack by C.M.B.
on surface ship (or submarine on surface). _A._ Object of attack
travelling in direction indicated by arrow _E._ _B._ The position of the
C.M.B. after delivering the attack. _C._ The torpedo, released by the
C.M.B. at point _D_, travelling on course ending at _F_, which, allowing
for movement of ship _A_, is the place where the torpedo should strike
its object of attack. From this it will be seen that the torpedo, when
released, actually follows the ship from which it is fired until the
latter swerves from the straight course, when the torpedo continues
until it strikes or misses the object of attack, the speed of the
torpedo being about the same or a little less than that of the C.M.B.
The total time occupied in such an attack over a course of two miles
would be about 2 1/2 minutes before the torpedo struck its object.]

The C.M.B. was a purely British design, and the firm largely responsible
for the success achieved was Messrs John J. Thornycroft & Company
Limited. There were bases for these sea-gnats at Portsmouth, Dover,
Dunkirk, and in the Thames Estuary at Osea Island. From all of these
points mid-Channel could be reached in less than thirty minutes.
Although useless in rough weather, a trip in a C.M.B., even on a calm
day, was sufficiently exciting. The roar of the engines made speech
impossible, and vision when sitting in the little glass-screened well,
or conning-tower, was limited by the great waves of greenish-white water
which curved upwards from either bow, and rolled astern in a welter of
foam. There was an awe-inspiring fury in the thunder of the 700 h.p.
engines revolving at 1350 per minute, and a feeling of ecstasy in the
stiff breeze of passage and the atomised spray. When waves came the
slap-slap-slap of the water as the sharp bows cleft through the crest
and the little vessel was for a brief moment poised dizzily on the bosom
of the swell caused tremors to pass through the thin grey hull, and, to
complete the review of sensation, there may be added the human thrill of
battle and the indescribable feeling of controlled power beneath one's
feet.

The C.M.B.'s record of service, although short, is nevertheless a
brilliant one. Towards the close of the year 1916 four of these little
vessels coming from the base at Dunkirk intercepted five German
destroyers returni