53 
PHYSICAL AND MATHEMATICAL SECTION. 
November 10th, 1864. 
Joseph Baxendell, F.R.A.S., President of the Section, 
in the Chair. 
Professor Clifton exhibited an acoustical electric telegraph, 
by which a note, sounded at one end of the line, is reproduced 
at the other end. 
He also pointed out the principles involved in the con- 
struction of this telegraph, viz. 
1st, The production of a sound whenever a current of suffi- 
cient strength commences to circulate round an electro magnet, 
or ceases so to circulate. 
2nd, The vibration of a stretched membrane in accordance 
with a note sounded near it. 
With respect to the second principle. Professor Clifton drew 
attention to the fact, that the researches of MM. Bourget and 
Bernard, in agreement with the mathematical investigations 
of Poisson and M. Lam£, show that a given square membrane 
will not vibrate in accord with any note , as stated by Savart. 
As the same is probably true of circular membranes, such as 
that used in this telegraph, it follows that only certain notes 
are capable of being transmitted by one instrument. 
