M. MELLONI ON THE TRANSMISSION OF RADIANT HEAT. 89 
is therefore a phenomenon entirely depending on the order which we 
have found to exist in respect to the calorific transmissions of diaphanous 
bodies, 
This. phenomenon now constitutes a striking relation between the 
properties of the caloric rays of the sun and those of the radiant heat 
of terrestrial bodies; but we shall see relations yet more intimate ap- 
pear between these two species of rays when we examine the alterations 
produced in calorific transmissions by changing the temperature of the 
radiating source. 
ARTICLE II. 
New Researches relative to the Immediate Transmission of Ra- 
diant Heat through different Solid and Liquid Bodies ; pre- 
sented to the Academy of Sciences on the 21st of April, 1834, 
and intended as a Supplement to the Memoir on the same sub- 
ject presented to the Academy on the 4th of February, 1833; 
by M. ME.ttont. 
From the Annales de Chimie et de Physique, t. uv. p. 337. 
Of the modifications which Calorific Transmissions undergo in consequence 
of the Radiating Source being changed. 
Tue experiments described in the former Memoir have shown that 
diaphanous bodies do not act in the same manner on the rays of heat 
and the rays of light simultaneously emanating from the most brilliant 
flame. We have seen, in fact, that thin flakes of alum and of citric 
acid, because of their transparency, perceptibly transmit all the luminous 
rays of an Argand lamp, and stop from eight to nine tenths of the ca- 
lorie ; while, on the other hand, thick pieces of smoky rock crystal inter- 
cept nearly the whole of the light and allow the radiant heat to pass 
freely. Do the different properties thus exhibited by each body, rela- 
tively to the two agents, and the relations of the calorific transmissions 
of the one screen to those of the other, remain constant, whatever be the 
source (luminous or obscure) whence the rays emanate? Such are the 
first questions that I have undertaken to solve in this second series of 
researches, 
That the comparison ttneen the quantities transmitted in each par- 
ticular case might he fairly made, it was necessary to operate upon rays 
