I am not able to give exact figures of the number of officers and men who were instructed in hydrophone work either at Hawkcraig or at other stations by instructors sent from Hawkcraig, but the total was certainly upwards of 1,000 officers and 2,000 men.

In addition to this extensive instructional work the development of the whole system of detecting the presence of submarines by sound is very largely due to the work originally carried out at Hawkcraig by Captain Ryan.
The first hydrophone station which was established in the spring of 1915 was from Oxcars Lighthouse in the Firth of Forth; it was later in the year transferred to Inchcolm.

Experimental work under Captain Ryan continued at Hawkcraig during 1915, and in 1916 a section of the Board of Invention and Research went to Hawkcraig to work in conjunction with him.

This station produced the Mark II directional hydrophone of which large numbers were ordered in 1917 for use in patrol craft.

It was a great improvement on any hydrophone instrument previously in use.
Hawkcraig also produced the directional plates fitted to our submarines, as well as many other inventions used in detecting the presence of submarines.
In addition to the work at Hawkcraig an experimental station under the Board of Invention and Research was established near Harwich in January, 1917.