892 
more recently, Savart found the means of preserving 
by transferring them to sheets of gummed paper. 
There are few experiments in physics of a more 
MATHEMATICAL AND PHYSICAL SCIENCE. [Diss. VI. 
musical notes. Previous duthors (for example, On the pro- 
Chladni, Biot, and Wollaston) having differed mate- 2uction of 
rially as to the range of audibility of repeated equi- — 
(438.) 
In bodies 
possessing 
unequal 
elasticity. 
(439.) 
Chaldni on 
meteoric 
bodies, 
striking character, or which so plainly reveal minute 
and complex motions so small and so rapid as to 
be difficultly appreciated otherwise. Mr Faraday 
and Mr Wheatstone have pursued the same enquiry 
experimentally, and the latter has satisfactorily de- 
duced the figures of Chladni’s square plates from the 
mechanical superposition of simple modes of vibra- 
tion which are symmetrical and isochronous. (Phil. 
Trans. 1833.) By so doing he has succeeded better 
than the mathematicians, whose results on this sub- 
ject have been very little practical. 
Chladni was the first to make experiments on the 
vibrations of bodies whose elasticity varies in dif- 
ferent directions. Thus he cut plates out of different 
kinds of wood, and found the nodal curves unsym- 
metrical in different directions depending on the 
course of the fibres. The experiments were naturally 
afterwards employed to illustrate the theory of ellip- 
soidal waves on the undulatory hypothesis of Optics. 
The experiments of Chladni procured for him the 
especial notice of Napoleon, by whose wish one of 
his works was translated into French. He died in 
1827, and besides his acoustical discoveries, he will 
be remembered by the sagacity and boldness with 
which he maintained the popular opinion of the 
fall of heavy meteors from the sky, contrary to the 
prevalent scepticism of philosophers, Chaldni’s suc- 
cess in establishing this important fact in natural 
history is due, like his other physical inductions, to 
distant impressions which affect the human ear as 
musical notes, Savart used a simple method, no 
doubt original to him, but anticipated I believe by 
Robison, in which a card is held near or touching 
a revolving wheel, and the number of impulses 
(each double) given to the air by every tooth as 
it passes the card, is readily measured. He thus 
found that a note occasioned by 24,000 double vi- 
brations in a second is perfectly audible; and, at 
the other limit of the musical scale, from seven to 
eight equidistant beats constitutes a sound having 
a distinct pitch. According to Savart, two conse- 
cutive double impulses of whatever duration are suf- 
ficient to convey to the ear the sensation of pitch. 
But a more elegant and accurate instrument for 
the numeration of sonorous pulsations is the Siréne Sirdne of 
of M. Cacniarp pz LA Tour, unquestionably one of M- Cagni- 
the most exact and satisfactory additions lately made ip,,,.. 
to our experimental apparatus. In it a current of 
air is repeatedly interrupted and renewed, giving 
rise to a series of impulses similar to those of the 
toothed wheel; and this apparatus is ingeniously 
contrived, so as to maintain its own motion, and 
record its indications. It is by far the most accu- 
rate known method of ascertaining the pitch of a 
given note. It may also be worked with water. 
Robison had also the merit of the primary idea of 
the Sirene, by making a stopcock revolve rapidly 
whilst applied to a tube emitting a blast of air. (3.) 
Savart extended the researches of Chladni by means Savart on 
of sand to many new cases, and with interesting sli pas 
results ; in particular he exhibited the effects of the solids, 
the constancy and simple-mindedness with which he 
attached himself to a strictly definite enquiry. 
(440.) We must not here enlarge upon the ingenious and 
Young— 
Robison. 
(441.) 
Savart. 
Propaga- 
tion of 
sound in 
masses of 
air, &. 
important investigations of Dr Thomas Young con- 
nected with acoustics. Being chiefly connected with 
his admirable Theory of Light, they will be noticed 
in the chapter on Optics. The peculiarly practical 
and sagacious views of Dr Robison connected with 
the Theory of Musical Instruments and Acoustics 
generally, must also be passed over. 
In Fexix Savart we find a man like Chladni who 
was especially devoted to a single and circumscribed 
branch of science—acoustics. His publishedresearches 
are almost all detached notices in the Annales de 
Chimie, with a few memoirs in the publications of the 
Institute; and whilst they are very interesting, exact, 
and instructive, I doubt whether it would be possible 
to place the results in a connected and comprehen- 
sive view before the reader. They are therefore rather 
to be sought in the special articles of the Encyclo- 
peedia devoted to the subject. In general they may 
be stated to refer to the following topics :—(1.) To 
the manner of propagation of sound through the 
air and through liquids, with an attempt to explore 
the manner in which sounds spread in apartments 
of different forms; an enquiry as difficult as it is 
important; (2.) To the generation and audibility of 
unequal mechanical elasticity of crystals cut in dif 
ferent directions. He has also examined with great 
care and ingenuity, the nature of the vibrations which 
occasion the accumulations of sand on the nodal 
lines of plates, and he comes to the conclusion that 
they are determined by simultaneous transverse and 
longitudinal movements (the latter of which are pa- 
rallel to the surface of the plate). In proof of this 
he shows that in long rods or hollow cylinders, the 
position of the nodes is intermediate and opposed 
upon the contrary sides of the rod or hollow cylinder. 
Savart made many experiments on the communica- 
tion of vibrations from one body to another ; showing 
that the molecular movements generally preserve 
their parallelism, so that a longitudinal vibration of 
one body may give rise to transversal movements in 
another ; and he applies this to the theory of musi- 
cal instruments. 
Savart was born at Meziéres in the department of 442.) 
Ardennes, on the 30th June 1791; and died some- Biographi- 
what prematurely on the 16th March 1840. He Ctl notice 
had some peculiarities of temper, amongst which 
was his unconquerable prejudice to everything Eng- 
lish. He did not even acknowledge the intimation 
