Portable Type.

Mark II.

Type.

Type.
Jul 31 2,750 500 - - Aug 31 2,750 700 - - Sep 30 2,750 850 - - Oct 31 3,500 1,000 - - Dec 31 3,680 1,950 870 37 HYDROPHONE STATIONS AND TRAINING SCHOOLS At the beginning of 1917 four _shore hydrophone stations_ were in use.
During the year eight additional stations were completed and several more were nearing completion.

The first step necessary was a considerable increase in the instructional facilities for training listeners both for the increased number of shore stations and for the large number of vessels that were fitted for hydrophone work during the year.
The greater part of this training took place at the establishment at Hawkcraig, near Rosyth, at which Captain Ryan, R.N., carried out so much exceedingly valuable work during the war.