and Transmission of Sound in Vater. 95: 
hammer of the weight of ten kilogrammes was used, fixed to 
a long iron handle, the upper part of which being above the 
water, was bent at aright angle; the summit of this angle 
was crossed by an axle-tree, to which the stalk of the hammer 
was suspended. This hammer, in all my experiments, was 
worked by one man, who could make a stroke every two 
seconds. 
I hoped to make, by means of this bell, a new series of ex- 
periments on the velocity of sound in the water of the lake, 
the mean temperature of which, measured between the two 
stations, was found to be 17° C., while by the observations 
made with much exactness in the month of November 1826, 
this temperature was 8°.1C. The ease with which we had 
heard strokes on this bell at the distance 35,000 metres, deter- 
mined me to choose this distance for the two stations. Mr. 
Muller, an astronomer connected with the observatory of Ge- 
neva, and Professor of Natural Philosophy at Nyon, assisted 
me in this experiment, and heard the sounds along with me,’ 
by means of a second apparatus. Unfortunately, during the 
only two days given us for the execution of our purpose, the 
clearness of the weather and the moonlight prevented us dis- 
tinguishing the lights produced by the burning of a pound of 
powder at each stroke, at the moment of the shock. 
This trial, made on the evening of the 5th August, between 
Promenthoux and Grandvaux, near Cully, has, however, de- 
monstrated to me the correctness of the views stated in my 
first memoir, respecting the utility that may result from this 
economical means of corresponding under the waters of the 
sea, at such distances that all other means of communication, 
by signal lights or sounds, conveyed by the air, cannot me 
made available. 
It now appears to me demonstrated that, in certain fayour- 
able localities, we may correspond under the sea, by means of 
very vigorous strokes and well combined acoustic apparatus, 
at a distance of some hundred thousand metres. 
It is very probable that, in seas of nearly uniform depth, 
the intensity of sound, far from diminishing in proportion to 
the square of the distance, only diminishes in proportion to 
the simple distance, or nearly so. I have already mentioned 
this property of the waves of sound, that when they are trans- 
