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52 EX P E R I M E N T S ON H E A R I N G IN WATER.
C H A P T E R IX .
EXPERIMENTS on HEARING in WATER.
AF t e r defcribing the ftrudurc of the ear in fiflies, I iliall give an account
of a few experiments I made, in 1780, on hearing in water, that we
may be able to judge better of the effect of found upon the ears
I employed two bells, tlie found of which I was ufed to ; one of them a fmall
tea-table bell ; the other much larger and thicker, fo that the found of it could
be very well heard at the diilance of a quarter of a mile.
When thefe were plunged under water and rung, I obferved that the found of
them was very fenfibly graver ; but ftill the ringing tremor of both was very diilinguiiliable.
On performing an accurate experiment, the tea-table bell was
found to found in air the higheft G of a common harpfichord ; but in water it
founded a fifth falfe lower, or it founded the C flaarp under the G.
I next plunged my head under the water while I rung the bell in the air, and
heard the found of it diftinclly. As the tone of the bell is louder and more
acute in the air than in the water, I need fcarcely obferve that its found is better
heard when the head of the perfon making the experiment' is under the
water and the bell above it, than when the bell is rung under the water while
the head is abovcTi;— —
I next plunged my whole body~l^--tH;&rfeeils^olding their handles in my
hands, under the water ; and then rung tliem, and was furprifed with the loudnefs
and diilinclnefs of their founds, and could readily diftinguifÎi their different
tones.
ïn like manner, "Vvhen, plunged under the water, I ilruck two ilones held in
jny hands againil each other, I was furprifed with the iliock communicated to
tlic cars.
I
T}ic iiigenious AbVé No!let has, about forty years ogo, publifhcd nn nccount of various experiments he made on
Ihis Tubjecl: " Le rcfultst cii a été, que non feuicment le bruit, quoique plus ou moins afToibli, fe tranfmcttoit h travers
" l'eau, mais encore l'efpece de bruit, les tons et les articulations <lc la voix liumainc (a)." And tlic cclcbratcd Dr li.
Franklin mentions, in ryûi, as his opinion (A), " That water will convey found farther and more readily than aii- ; be-
" caufe two ftoncs being ftrucic fmartly together under water, the flroke may be hearil at a greater diftaiice by an car pla-
" ccd alfo under water in the fame river than it can be heard through the air. He thinks he has heard it near a mile ;
" how mucii farther it may be heard he knows not i but fuppofes a great deal farther, becaufe ilie foun<l did not feem
« faint, as if at a diftance, like iliftant founds through air, but fmart and ftrong, and as if prefent juil at the
. ear (i)."
(,;) Sec Hift. ic I'Aead. R. d« Sciences 1743, p. 26. ct Mem. p. igg. &e.
(i) ¿it Letters, &c. by Dr B. Franklin, L, \\W. dated July 20. 1762.
E X P E R I M E N T S ok H EAR ING in WATER. .53
I afterwards, by means of a firing tied to the handle of the largefl bell, and
to an inflated bladder, fufpended that bell in a very deep pool, fix feet under
the farface of the water, and took hold of a cord twelve yards long, which I
had before tied to its handle. I then plunged under the water arid pulled the
cord, and found that the found was inflantly conveyed to rhy ears.
In the laft place, I thought of trying an experiment, to determine whether
air or water coaveycd found quickeft: but as we have no lake near Edinburgh
above eight hundi-ed feet broad, I found it impoffible, independently of the difficulty
of conflrucling a proper apparatus, to perform an experiment in a decifive
way.
It may however be worth while to niention one trial I made. I charged three
Engliih-pint bottles each with about ten bunces of gunpowder. I then inferted
a tin-tube four feet in length into each bottle, and prevented the water from
getring into the bottle by wrapping a piece of wet bladder around the neck of it
and the end of the tube which entered into it, and tying the tube and neck of
the bottle to cach other.
After filling the tube with gunpowder, I fixed to the top of it a picce of
match-paper ; and into the match-paper, juft over the top of the tube, I put
two ounces of gunpowder.
1 then funk the bottle near the lide of a lake to the depth of about two feet,
and went into the water at the greateft diilance poffible, which was about eight
hundred feet, and laid myfelf on my back in the water, with my ears under its
furface, and nofe and eyes alone above it. The match was then fet fire to by
another perfon ; and as it was midnight, I faw the flafh of the gunpowder contained
within the match, and foon after heard the noife of the explofion of the
powder within the bottle. But I found it was impofTiblc in this way to determine
the velocity of the found with accuracy ; for the gunpowder within the
bottle was not fet fire to through the tube To inftantaneouny as I had expelled.
When the powder contained within the rriatch-paper of the fécond and third
bottles took fire, I plunged myfelf entirely under water.
Upon the whole, befides not being provided with a proper apparatus, and
not having acccfs to a piece of water of fufiicient extent, this experiment was
not repeated often enough : So that all the conclufion I could draw Was, that after
the Ijottle buril, I heard one,, but did not hear two cxplofions ; fo that the
water feemed to convey the found in nearly the fame time as the atmofphere
•
• A good method of making fuch an experiment would bc, to fufpend under water, in a broad lake, a very large and
ioud-founding bell, fuch as is ufed ill diurh-flecples, and for one perfon to ftrike tliis with an iron-hammer, between the
h;uidle of which and the trigger of a mulket, or cannon fitted with a lock, a rope was ftretched} wliile another perfon
xfas ftationed at tlie diftance of :i miie or more, with one or both ears under the water.
liy tliis means, as two very diiïercnt founds would be produced at the fame inftant, tlie one in air and the other in
water, it might be obfevved which of them iiruck the ear fooneft. Befides tliis, the flafii ihowing t!ie exail time at which
ilic bell «'as (huck, the velocity of foUml in t]ie water might be accurately determined,
m