96 M. Daniel Colladon’s Experiments on Transmission of Sound. 
mitted in water and meet the surface under a very acute angle, 
they become entirely reflected into the fluid mass. A great ex- 
tent of water, varying little in depth, represents a liquid plate, 
whose two surfaces, the upper and the lower, concentrate and 
throw back into the interior of the fluid almost the whole of 
_ the vibrations which happen to meet these surfaces under very 
acute angles. 
It may be perceived that, in the bottom of gulfs, the vibra- 
tions, moved by the tide and concentrated on certain points, 
may produce a very intense sound. It is easy, moreover, to 
conceive a multitude of arrangements and artificial construc- 
tions which would facilitate these telegraphic experiments, 
from which nautical men will derive advantage sooner or later. 
The agitation of the waves very little disturbs the nearly ab- 
solute silence which reigns under the waters of the sea, and 
does not impede the transmission of sound ; this silence should 
likewise favour the communications which may be attempted 
to be established under water.* 
At the distance of 35,000 metres (about nine leagues by 
land) each stroke given to the bell was distinctly heard with 
the two apparatus with which we were provided. One of 
these instruments was the same that I employed in my experi- 
ments in 1826 ; the sound by it seemed distinctly defined and 
short. With the other instrument, improved, the sound was a 
little more prolonged ; we were conscious of the tingling of the 
bell, and could pretty well distinguish its tone. 
Neither Mr Muller nor myself could hear any echo, although 
the configuration of the lake led us to suppose that we would 
hear many. But Mr Veret, an old pupil of the central school, 
who during these experiments was moving about in a boat 
with an apparatus for hearing perpendicularly at the shore 
some thousand metres from the vessel in which the bell was 
placed, heard two distinct echoes in certain stations. For the 
most part, when placed in a similar situation, one heard only 
® The sound of waves does not prevent us distinguishing strokes on a bell, 
provided the construction of the instrument be such that the water glides 
upon its surface without directly dashing against it. It is for this reason 
that the form adopted by Mr Bonnycastle, in his experiments in 1838, appears 
to me disadvantageous, 
