70,359
May - 589,754
June - 675,154

Because of the time required for production, it was a sheer
impossibility to _put into effect_ any fresh devices that might be
adopted for dealing with submarine warfare for many months, and all that
could be done was to try new methods of approach to the coast and, as
the number of small craft suitable for escort duty increased, to extend
gradually the convoy system already in force to a certain extent for the
French coal trade and the Scandinavian trade.

In the chapters which follow the further steps which were taken to deal
with the problem, and the degree of success which attended them, will be
described.

CHAPTER III

ANTI-SUBMARINE OPERATIONS

The previous chapters have dealt with the changes in organization
carried out at the Admiralty during the year 1917 largely with the
object of being able to deal more effectively with the submarine warfare
against merchant ships. Mention has also been made of the submarine
problem with which the Navy had to deal; particulars of the
anti-submarine and other work carried out will now be examined.

A very large proportion of the successful anti-submarine devices brought
into use during 1917, and continued throughout the year 1918, were the
outcome of the work of the Anti-Submarine Division of the Naval Staff,
and it is but just that the high value of this work should be recognized
when the history of the war comes to be written by future historians. As
has been stated in Chapter I, Rear-Admiral A.C. Duff, C.B., was the
original head of the division, with Captain F.C. Dreyer, C.B., Commander
Yeats Brown, and Commander Reginald Henderson as his immediate
assistants. Captain H.T. Walwyn took the place of Captain Dreyer on
March 1, 1917, when the latter officer became Director of Naval
Ordnance. When Admiral Duff was appointed Assistant Chief of the Naval
Staff, with a seat on the Board, in May, 1917, Captain W.W. Fisher,
C.B., became head of the division, which still remained one of the
divisions of the Staff working immediately under the A.C.N.S. It is to
these officers, with their most zealous, clever and efficient staff,
that the institution of many of the successful anti-submarine measures
is largely due. They were indefatigable in their search for new methods
and in working out and perfecting fresh schemes, and they kept their
minds open to _new ideas_. They received much valuable assistance from
the great civili