and Transmission of Sound in Water. 93 
scribed has the power of increasing those transmitted by water 
to an unknown extent, and which my recent experiments have 
proved to be much beyond what I had previously ascertained. 
I possess an apparatus, the amplifying power of which is more 
than double that of the instrument I formerly used, and I am 
certain that I can still further augment it. 
I have had an instrument constructed for me with a horolo- 
gical movement, and a bell of somewhat less than a kilogramme 
in weight; a hammer moved by the watch strikes the bell by 
the action of a spring in a continual state of tension. I have 
likewise made use of a small musical box, which plays under 
water, whether it be sunk without a covering, or enclosed in a 
small diving-bell. It is with these two instruments that I 
have obtained the results I am about to announce. Among 
other facts, I have ascertained that shrill sounds can be more 
easily heard under water at great distances than such as are 
of a deep tone. 
Vessels formed of very thin metallic plates, the latter closed 
at the bottom, form undoubtedly the most suitable hydro- 
acoustic apparatus ; but all kinds of solid bodies, partly sunk 
in water, and to which the head is applied for the purpose of 
hearing, may transmit to the ear sounds propagated under 
water. 
When a sonorous body is put into a state of vibration under 
water, its vibrations, far from being speedily extinguished, 
may continue for a pretty long period, even although the den- 
sity of the sonorous body and that of the water be nearly the 
same. Thus, by striking a small crystal bell of 18 centime- 
ters at the opening, so as to make it vibrate under the water, 
we can satisfy ourselves, after the lapse of a second, that 
the vibrations still continue, although no sound be heard, for 
if we then withdraw the bell from the water, a very distinct 
sound is perceptible. A large metallic bell entirely submerged 
produces, when struck, a sound which continues for many 
seconds ; by placing a bar in the water at a little distance 
from the bell, and at the same time holding it in the hand, we 
feel a very violent vibratory movement which is transmitted 
by the water to the bar. 
The intonations of the voice may be transmitted to some 
distance under water; but if the person speaking is placed 
