ACOUSTIC TELEGRAPHY. 
25 
pagation of sound in the pipes which carried the water from 
the pump at Ohaillot, and, it is stated that with three hundred 
pipes of a thousand toises each, despatches could be sent one 
hundred and fifty leagues in fifty minutes. In 1783, he 
published at Philadelphia a prospectus which shows that he 
had proposed to the Academie des Sciences absolutely new 
methods of sending a despatch with great speed. 
The two discoveries were examined by the Academie, and 
MM. Condoret and Milly, the commissioners appointed to 
report upon them, stated in their report dated 15th June, 
1782, that as regards the first discovery, the means proposed 
appeared to them practical, ingenious, and novel; “ that it had 
no resemblance to any methods previously proposed, and that 
by it a signal might be given at a distance of thirty leagues in 
a few seconds and without intermediate stations; that the 
apparatus would be neither expensive nor cumbersome, and 
that they had appended to Dom Gantey’s paper the grounds 
of their belief in the possibility of the method, which the 
author wished to keep secret.” This secret was, in fact, placed 
under seal, and doubtless still remains in that condition in the 
archives of the Academie des Sciences. 
The same commissioners were appointed to report upon 
the second method ; but Gantey asked them to postpone their 
examination of it until he had obtained the money for making- 
some experiments in their presence. He opened a subscrip¬ 
tion, which proved inadequate for the expense that would be 
incurred in the trials he wished to make, and the Report was 
never presented. 
M. Biot devoted some attention to the investigation which 
Dom Gantey intended to make. He read a paper before the 
Academie des Sciences, containing an account of several 
beautiful experiments on the propagation of sound through 
solids, and through air contained in very long tubes. He 
showed that sound is propagated in solid bodies more rapidly 
than in air, and he estimated the difference with a sagacity 
and precision that exemplify the exactitude of observation 
introduced into modern physics. 
Sound is of great service in telegraphy. It is well known 
that from the sounds made by the Morse key or by the 
receiving apparatus the despatches may be read by the ear alone. 
