The trials were therefore continued, and as a result, in June, 1917, a further order was issued to the Fleet, giving directions as to the type of projectile to be used against submarines from all natures of guns, pending the introduction of delay 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.