due to two causes: (1) the inexperience
of their deck officers owing to so many of them having been taken for
the Royal Naval Reserve, and (2) the inexperience of their engineers,
combined with the impossibility of obtaining delicate adjustments of
speed by reason of the absence of suitable engine-room telegraphs and
the poor quality of much of the coal used. When pressed as to the
greatest number of ships that could be expected to manoeuvre together in
safety, the masters of these cargo steamers, all experienced seamen,
gave it as their opinion that two or possibly three was the maximum
number. The opinions thus expressed were confirmed later by other
masters of merchant ships who were consulted on the subject. It is to
the eternal credit of the British Merchant Marine, which rendered
service of absolutely inestimable value to the Empire throughout the
war, that when put to the test by the adoption of the convoy system,
officers and men proved that they could achieve far more than they
themselves had considered possible. At the same time it should be
recognized how severe a strain was imposed on officers, particularly the
masters, of vessels sailing in convoy.

The matter was kept constantly under review. In February, 1917, the
Germans commenced unrestricted submarine warfare against merchant ships
of all nationalities, and as a consequence our shipping losses, as well
as those of Allied and neutral countries, began to mount steadily each
succeeding month. The effect of this new phase of submarine warfare is
best illustrated by a few figures.

During the last four months of 1916 the gross tonnage lost by _submarine
attack_ alone gave the following monthly average: British, 121,500;
Allies, 59,500; neutrals, 87,500; total, 268,500.

In the first four months of 1917 the figures became, in round numbers:

British. Allies. Neutrals. Total.

January 104,000 62,000 116,000 282,000
February 256,000 77,000 131,000 464,000
March 283,000 74,000 149,000 506,000
April 513,000 133,000 185,000 831,000

(The United States entered the war on April 6, 1917.)

NOTE.--In neither case is the loss of fishing craft included.

It will be realized that, since the losses towards the end of 1916 were
such as to give just cause for considerable anxiety, the later figures
made it clear that some method of counteracting the submarines must be
f