pply ships for the Grand Fleet were nearly always under
escort. The area from the Scotch to the German coast was looked upon
more as a possible battle-ground for the fleets at war than as a route
for merchant shipping, owing to the comparatively few big commercial
harbours along the eastern shore.

Laying the moorings of over 150 gigantic buoys in fairly deep water,
exceptionally prone to sudden and violent storms, was in itself a
noteworthy feat of submarine engineering. The chains and anchors had to
be of great strength, and the whole work, which occupied many weeks, was
carried out in waters infested with submarines and mines.

The task of sweeping this vast stretch of sea almost continuously for
four years was by no means either straightforward or without risk. The
Germans, when they discovered the existence and purpose of this channel,
sought to turn it to their own advantage by systematically laying mines
around the moorings of the mark-buoys, where they could only be swept up
with great difficulty, owing to the sweep-wires fouling the moorings of
the buoys. This strategem had to be answered by the creation of "switch
lines," or small sections of false channel marked by buoys, while the
real channel was only outlined on secret charts. In this way the
preservation of the war channel and its use for misleading and
entrapping U and U-C boats became a semi-independent campaign, in the
same way as that which surrounded the great mine barrages and other
activities of the anti-submarine service.

MINE PROTECTION DEVICES

It is an axiom of war that new weapons of attack are invariably met by
new methods of defence. The mine was no exception to this rule, although
up to the present time the various antidotes are in all cases only
partial remedies. During the years of war, with the brains of a maritime
nation focused on the subject, there were naturally many devices
suggested and tried for protecting ships from mines. The great majority
of these suggestions may be classified in two groups: (1) Those which
sought to deflect the mine from the pathway of the ship; and (2) those
which sought to minimise the result of the explosion. One method from
each of these groups was adopted with various modifications to suit
different classes of ships.

In the first group came the _Paravane_, which had as its basis the
suspension of a submerged wire around the bow of a ship, which caught
and deflected the mine-mooring wire before t