elay action fuses for the smaller guns; this was the
temporary solution of the difficulty until a new type of shell evolved
from the experience gained at the trials could be produced and issued.
The trials, which were exhaustive, were pressed forward vigorously and
continuously throughout the year 1917, and meanwhile more accurate
information as to the exact form of the hull and the thickness of the
plating of German submarines became available. Early in 1918 the first
supplies of the new fuses were ready for issue.

SMOKE APPARATUS

The earlier _smoke apparatus_ for supply to merchant ships was designed
towards the end of 1916.

One description of smoke apparatus consisted of an arrangement for
burning phosphorus at the stern of a ship; in other cases firework
composition and other chemicals were used. A dense smoke cloud was thus
formed, and, with the wind in a suitable direction, a vessel could hide
her movements from an enemy submarine or other vessel, and thus screen
herself from accurate shell fire.

In another form the apparatus was thrown overboard and formed a smoke
cloud on the water.

The rate of supply of sets of the smoke apparatus to ships is shown by
the following figures:

April 1, 1917 - 1,372 sets
July 3, 1917 - 2,563 sets
October 5, 1917 - 3,445 sets
November 26, 1917 - 3,976 sets

DEPTH CHARGES

_Depth charges_, as supplied to ships in 1917, were of two patterns:
one, Type D, contained a charge of 300 lb. of T.N.T., and the other,
Type D*, carried 120 lb. of T.N.T. At the commencement of 1917 the
allowance to ships was two of Type D and two of Type D*, and the supply
was insufficient at that time to keep up the stock required to maintain
on board four per destroyer, the number for which they were fitted, or
to supply all trawlers and other patrol craft with their allowance. The
great value of the depth charge as a weapon against submarines, and the
large number that were required for successful attack, became apparent
early in 1917, and the allowance was increased. Difficulty was
experienced throughout the year in maintaining adequate stocks owing to
the shortage of labour and the many demands on our industries made by
the war, but the improvement is shown by the fact that while the average
output _per week_ of depth charges was only 140 in July, it had become
over 500 by October, and that by the end of December it was raised to
over 800, and was still increasing very rapid