Evening star., 1926-10-24
By WILLIAM J. WHEATLEy.

floors as steamers pass over
" the surface above is being
made possible by the devel-
opment of radio apparatus
A vessel may send out a radio spark
and get it's echo hack on an instru.
ment which picks up sounds not
audible TO the human ear.
Vessels now can come into harbor
day or night. and can instantane.
ously determine the exact amount of
water under them. no longer being
compelled to wait for the leadsman
in the ''chains" to fix the distance.
BY means of this apparatus. being
developed AT the Nays scientific
laboratories at Bellevue. u. c., 1t
has been possible to get picture of
the beds under waterways more ac-
curately than is possible by the in
tricate survey operations heretofore
necessary. and it can be done at con-
siderably lower cost.
The apparatus was born of" war
necessity. when it became necessary
to determine the positions of the
enemy >uoma arines. by listening for
sounds coming through the water
from TIL. propellers and motors.
These we're developed to fine point
during the late war. but now come
the 'supersonics," a new field of radio
possibilities for making water travel
more safe.
The term "supersonics" refers to
frequencies above the limits of au-
dibility of the human ear. For in
stance. the human ear may be con-
sidered a receiver, tuned to recognize
sounds lying between frequencies of
80 to 10000 cycles per second. Sounds
lying above this soectr"m are inau
dible and he ro"ention of these
sounds is arccn,,,ije' 'c' by the use
OF the heterodyne principle.
Through the ''~a Of short waves 1t
has been possible to telephone under
water and 10 te!egra ph at speeds Of
% to 30 words per minute. This Is
considered by scientists an advance
over the older met hods OF audible
transmission and reception under
water. At present many scientists,
both I'm this country and overseas q
are engaged in further development
Of this field
Considerable progress has been
made in the prosecution of under
water sound resear' h. as we'll as in
Its development and practical design,
hy the Navy Department in order to
meet It's needs in this fed Under
the director of the Naval Research
La horatory al Reilevtle, -. G.. a sound
division hast haai established, with
DR.. Harvey {. Hayes as superintend
ent He is assisted by DR.. f. B.
Stephenson. physicist.
In addition to the usual labora tory
equipment. two harces have been
assigned to the division. ard these
have been provided Wi h instruments
for conducting experimental tests
In sound transmission and reception.
Jor
with limited living quarters for the
use of the personnel when opera tions
are being carried on away from the
laboratory. A harbor tug. with bat
terry charging plant. is being used for
moving one of the test harges to diff
ferent locations in connection with
the range tests of the superSonic
transmitters.
nNE of the latest devices developed
a the Washington Navy Yard is
suitable for use with sound trans
mitters of any frequency above 500
cycles. including supersonics. 1t is
so designed that the depth Is indi-
Gated on dial and at the same time
recorded on a moving paper record
which adapts Itself to the use of re-
peaters at remote parts of the ship.
BY means of this apparatus, for
instance. a captain could remain in
his cabin while his ship was entering
New York harbor or travelling over
the Great Lakes and know every
minute just how much water he was
In. and by comparison with the
charts. could tell whether he was
heading right or wrong. no, matter
what the weather was on the outside.
Or repeater in the engine room
would keep the engineer informed as
to whether he had enough water
under him to make it safe to MAIN
tain suctions
The graphic acoustic" sounder is
designed for use with sound trans
mitters and receivers employing fire.
Quenctes of son cycles or more. but