The San Francisco call., 1896-11-15
Phonote1emeter Watch.

officer will be able to order the elevation or de-
preston of his guns TO the correct degree by
the indications of the watch, which is so
small that 1T can be carried in the waistcoat
pocket like an ordinary timepiece.
Holding the instrument in his left hand .the
officer watches for the flash of the eneIny's
the light he presses screw. which resembles
that OF a keyless watch. When he hears the
report he presses the screw a second time. In
the interval between the two pressures a
needle or hand has moved over an arc on the
face OF the instrument This face registers
fifteen seconds, each second being divide into
ten parts. There is, moreover, small dial on
the back, which registers the number of times
that the needle has gone round and marks in-
simultaneously the minutes and quarter min
utes.
Within the circle OF seconds is a smaller
one, which indicates the distance covered by
the sound through the air. The approximate
distance at which the weapon was fired is
thus seen at a glance. The same thing hap
pens in the case OF flash OF lightning which
precedes clap of thunder.
The graduation is easily made. The velocity
OF light is 100000 kilometers a second. This
is the number most nearly concording from
astronomical and direct physical methods.
During the same lapse OF time sound travels
$50 meters, velocity ofabout million times
less than that of light. The propagation of
light is practically instantaneous.
With this knowledge, and knowing the time
that eiapses before the sound is heard, it is
easy to calculate the distance at which the re-
port originated.
This discovery was made in 1922, when sew
eral French academicians measured at Vile
luif and Montlhery the time between the mo-
ment they perceived the flash of q gun fired
from the opposite fort and the moment the
sound of the report reached their ears. Know
ing the distance between the two places
twenty-five kilometers-they merely had to de-
duct the velocity of the sound.
The value of Captain Thouvenin's invention
to an army using it in time of war is obvious
to any one. Very much must depend in these
days of appallingly destructive long-distanoe
weapons, single discharge from which may
wipe whole regiment out of existence, upon
getting the guns to do effective work quicker
tn an the enemy is able TO do. 1t is conceded
that the great wars of the future will be
mainly duels between artillery. The phono-
telemeter watch will enable commanders of
batteries 10 promptly concentrate their fire
without having to experiment TO find range,
as in times past. This enormous advantage
might be sufficient 10 decide battle.
In the event of a night attack by infantry
the new instrument will enable the defending
machine-guns to vomit their ceaseless hail of
projecti.es upon the exact spot from which the
enemy's rife-fring begins and to keep the
rauge upon the advancing regiments, so that
every turn of a crank will put many men hors
de combat.
At sea. when battle-ships moving at full
speed offer difficult target to each other, q
vessel steaming parallel with another in the
same direction and having the distance be-
tween them exactly indicated at the outset of
the engagement may be able 10 concentrate
her whole broadside with unerring aim and
sink the hostile ship before the latter can find
the range or ct least infiict such damage upon
her to place her in position OF hopeless
inferiority.
The phonotelemeter will also be of the ut
m ost value at the coastguard and liieboat sta
tions in case of vessels in distress firing signal
guns for help, and may be the means of saving
innumerable lives. The men who work the
rocket apparatus frequently fail to judge the
distance between them and ship in distress,
and in consequence the line falls short The
inventor of the new instrument for judging
distances claims that it can gauge distance so
closely that the men engaged in saving the
lives of wrecked mariners will know just how
far to throw the lie line at the first cast.