ped through the
water. Thus the target against which they were launched achieved its
own destination. They were fitted with small gyroscopes to keep them
straight until the magnetic-heads began to exert a dominating influence.

Amidships was the conning-tower, with its four searchlights, so
arranged as to be capable of being used singly or together. Thus it
was possible to illuminate the waters for half a mile in every
direction. Above the conning-tower were two collapsible periscopes,
and beneath it the central ballast, beneath which lay the charge of
T.N.T. that John Dene had boasted would send the _Destroyer_ to Kingdom
Come should she ever be in danger of capture.

Abaft the conning-tower were the engines, a switchboard, and finally
the berths of the engine-room staff. For'ard of the conning-tower were
the berths of the crew, and still further for'ard were those of John
Dene and the officers. John Dene's invention of a new and lighter
storage-battery had enabled him to control the _Destroyer_ entirely by
electricity. She possessed an endurance of fifteen-hundred miles, and
as for the most part she held a watching brief, this would mean that
she could remain at sea for a month or more.

Her speed submerged was fourteen knots, which gave her a superiority
over the fastest German craft, and she could remain submerged for two
days. She could then recharge her compressed-air chambers without
coming to the surface by means of a tube, through which fresh air could
be sucked from the surface, and the foul discharged. These were
weighted and floated in various parts in such a manner that they could
be thrown out in a diagonal direction. The object of this was to
protect the _Destroyer_ from depth-charges in the event of her
whereabouts being discovered by an enemy ship, which would render it
dangerous for her to come to the surface.

"The _Destroyer's_ a submarine," John Dene had remarked, "and
submarines fight and live under water and not on it."

Consequently in designing the _Destroyer_ he had first considered the
special requirements entailed by the novelty of the methods she would
employ. She had deck-guns, periscopes and torpedo-tubes; but they were
in every sense subsidiary to those qualities that rendered her unique
among boats capable of submersion, viz., her searchlights and her
magnetic projectiles. Under water there were only two dangers capable
of threatening her--mines and depth-charges. Prope