ree bases of the British Isles amounted to 3400, of which
over 1000 stand to the credit of the Harwich base. It is a notable
fact, too, that in the same year 500 mines were destroyed
consecutively in this area without the loss of a single merchantman,
whereas the average for the United Kingdom had been one merchantman
lost to thirteen mines destroyed.

CHAPTER XII

WORK OF THE AUXILIARIES

CHAPTER XII

WORK OF THE AUXILIARIES

Mine-sweeping methods--Indicator nets--Heavy
losses--Brilliant rescues.

Without going into technical details, I will now give a brief
explanation of the usual methods employed by the mine-sweeping
trawlers of the Harwich base. Two trawlers steaming abreast at about
four hundred yards distance apart tow a sweep wire eight hundred yards
in length, an end of which is attached to each trawler. The wire thus
drags astern in a great loop, which is kept at the requisite
depth--that is, at a depth well exceeding the draught of the deepest
ship which would travel across that area--by kites. This sweep wire
is serrated, so that when towing it quickly saws through the moorings
of the mines, which are thus released and rise to the surface. When
two or more pairs of trawlers are sweeping in unison they adopt what
may be termed an echelon formation. The second pair of mine-sweepers
follows the first pair, at a safe distance astern, on a parallel
course, but on an alignment that causes the space swept by the
following pair of vessels to somewhat overlap that swept by the
leading pair, so that no unswept space is left between the two. If a
third pair of vessels follows, it takes up a similar position astern
of the second pair; and so on, if there be other pairs engaged in the
sweep. When a strong cross tide is running, to carry out this
operation accurately is no easy task. But the skilled North Sea
fishermen who man the trawlers are the right men for this sort of
work. They rapidly acquire all the tricks of sweeping, and soon learn
to detect a mine that has been caught in the sweep by the singing of
the sweep wire, the feel of it, and other delicate signs. The
mine-sweeping trawlers are accompanied by a vessel whose duty it is to
sink or explode by rifle fire the released mines as they appear on the
surface.

The above explanation of mine-sweeping, of course, deals with very
elementary matter. For during the war this science has made immense
progress, and volumes could be writ