Untitled

INTRODUCTION 9
giving effect to the programme already outlined.
In the New Year the Admiralty passed the
construction of ten more shore stations at
home and abroad, and six sound-ranging
stations.
We now reach the era of the rubber ' eel ' and
c
'
porpoise hydrophones.
Both these instruments spelt a new departure.
They could be towed from the stern of a vessel
under way a marked advance and furthermore
the latter instrument was a direction
indicator.
The cables originally used with both types
were rubber-covered, instead of having the usual
creosoted hemp covering of the tripod variety.
Although they were particularly heavy, they
were not so steady in the water as the type which
replaced them. Occasionally their undulatory
movement would create a vibration, reproduced
on the telephone receivers, which it was necessary
to eliminate from the mind.
The tripod type of cable was also used, but
though more satisfactory in operation than the
last mentioned, it fell short so it was agreed -
of the open braided plait cable.
Those who used
this cable under all conditions of weather supposed
that the partial percolation of the water,
through the open plait, had a ' holding up ' or
steadying effect on the towline.