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 rapidly.

As a consequence, early in 1918 it was found possible to increase the supply very largely, as many as 30 to 40 per destroyer being carried.
Improvements in the details of depth charges were effected during 1917.
One such improvement was the introduction of a pistol capable of firing at much greater depths than had been in use before.

The result was that all vessels, whether fast or slow, could safely use the 300-lb.

depth charge if set to a sufficient depth.