370 Miscellanies. 
with the same result. These facts M. Darcet thinks ought, at least, 
to induce the Academy to suspend its judgment, before it harbors a 
sentiment unfavorable to the wholesomeness and economy of gelatine. 
Rev. Encyc. Juin, 1831. : : 
28. New instruments for measuring heat.—On the 5th of Septem- 
ber, MM. Nobili and Belloni presented an instrument of their inven- 
tion, whieh they called a thermo-multiplicateur, by means of which 
ey are able to appreciate changes of temperature, so small as to be 
undiscoverable by any other instrument. The principal piece of the 
instrument is composed of thirty eight elements, (antimony and bis- 
muth,)-united in very acute angles. The second piece is a galvano- 
meter of two needles, particularly adapted to a thermo-electric cur- 
nt. The instrument, therefore, depends upon electro-magnetic 
changes, which are themselves consequent upon the changes of tem- 
perature, which the instrument is thus intended to indicate. 
ne of their first trials with the instrument enabled them to dis- 
cover a serious imperfection in all the thermoscopes in common use. 
en a plate or blade of glass is exposed to the sun or any other 
source of radiant heat, a portion of the heat passes immediately _ 
through the transparent body, but another portion is arrested by the 
first strata, and being there accumulated it advances by degrees to 
the posterior surface. The first portion is so much less in relation 
to the second as the temperature of the source whence it issues is the 
less elevated ; the result evidently is, that if the rays proceed from 
a very feeble source, this first portion is reduced to almost nothing. 
Those thermoscopes, therefore, which are covered (as they nearly 
all are) with a cage of glass, are placed under very unfavorable cir- 
cumstances. The new instrument is not subject to this difficulty, 
and in consequence it indicates the instantaneous passage of a body 
slightly warmed, while the thermoscope of Reaumur remains com- 
pletely insensible. 
general, the instantaneous passage of calorific rays through 
transparent bodies, depends on their degrees of transparency, and 
this relation appeared constant in all the substances which they first 
tried, viz. sulphate of lime, mica, oil, alcohol and nitric acid; but 
he law was found to be completely at fault with respect to water- 
This liquid, in fact, as the authors found, intercepts the instanta- 
neous passage of the calorific rays and stops it completely ; so that, 
however thin the stratum may be, when such a diaphragm is inter- 
* . 
