Evening star., 1926-10-24

when using the hand lead or other
Of the weight-andl line types of sound
ing machinery.
However the accuracy and reliability
of the "angle method" depends so
greatly upon the expertness OF the
operators of sound apparatus that
duce the factor of human error has
been undertaken. and in this problem
the Navy has met with no small de-
gree Of success.
The time elapsed between the ennis
sion of sound and the reception OF
an echo under water, as measured by
a stop-watch. can be employed to de-
termine approximate depths. and this
fact has been the basis of the devel-
opment of the sonic depth-flnders
which are now In use on many YES
sells OF the United States Navy and
other Government departments.
The use Of stop.watches. the best
Of which measures time 10 the tentn
Of a second. in determining the sound
time interval In sounding Ia limited
In actual practice TO the greater
depths-that is. more than 40 fathoms.
A fathom is six feet, and sound In
water travels about 4.SO0 feet. or SOO
fathoms. second. With the best stop.
watch, marking the shortest interval
Of one-tenth Of u second. there would
be a liability Of an error, therefore, OF
80 fathoms, or One-tenth or second.
The sound must come from the ship.
go to the bottom and be reflected back
to the ship: the total travel of the
sound would be so fathomS or an
actual depth Of 40 fathoms.
The difficult problem which the Navy
had to solve was the development Of
a device that would measure the time
intervals in sonic sounding within the
limits Of one-four- -hundredth of a sec
ond, or the time required for SOUND
to travel two fathoms through water
The error Of such a device in measur-
ing depth would he then reduced to
one fathom.
In 1921 the Engineering Expert
ment Station at Annapolis, Md. pro
duced the first model of a sonic
depth.inder which met the require
ments in depths from 40 to 1000
fathoms. This model was finally In
stalled on a destroyer, and with II
a line of sounds was made from New
mort. r. l.. across the Atlantlc,
through the Mediterranean and Red
Seas, eastward to Chefoo. China, ana
thence to Manila. Philippine lsla amos:
Similar or improved devices Installed
on other vessels Of the Navy have
sounded the Pacific from San Fran
cisco to Hawaii and Australia: still
others have sounded the Atlantic ana
Pacific on the normal routes from
Boston to Seattle. through the canal,
until II NAV be said that the Navy,
by this means, has completed chain
Of soundings reaching around the
world, all made during the ordinary
cruising of the vessels.
THE largest consecutive survey OF
Il any part of the ocean bed ever
undertaken was accomplished by Two
destroyers fitted with sonic depth
finders In 1922. when an area reacn-
ing from San Francisco to San Diego
and from the coast approximately ~
miles seaward was sounded WIN
sonic depth finders. The purpose OF
the survey was to obtain the topograr
nhv of the ocean bed along the CONT.
mental shelf in order that interested
scientists and scientific societies
might study the causes or eartn-
quakes along the California coast.
The destroyers steamed $500 miles
at 12 knots during this undertaking,
sounding the entire area OF 34.oOo
square miles in a little more than a
month. With the old methods OF
We1Rnt-anQ-llne BOuHullSS tAl5 "uA
vey would have required several
years at a tremendous increase In
cost.
The result Of the work done by
these two destroyers. the Hull and
Cory, amounted to practically a. pho
tograph Of the oceans bottom over
this immense area. Every little
mound on the bottom showed In
much more distinct form than ever
could be shown by employing the
old methods.
The Navy recently was called upon
to survey the route of the War De
partment's submarine telegraph
cable which serves Alaska. This
cable has given considerable trouble
for many years because breaks fire.
ouently occurred where 1t was laid
over submerged mountains and across
valleys off the rocky coast Of Van
couver and Alaska.
The survey of the ocean bed along
fCnnftpua6 np Fifth Pa0AN