and the Mode of its. Communication. ijg 
of the same means : but, if those radiations be caloric , emitted 
by those bodies, (which the hypothesis in question supposes,) 
how did it happen, that the ball of the thermoscope, instead of 
being more heated by the additional quantity of caloric which it 
received in consequence of the blackening of the disk A, was 
actually more cooled ? 
It may perhaps be said, by the advocates for the hypothesis 
in question, that the blackening of the surface of the disk A, 
caused a greater quantity of caloric to be sent off to it by the 
ball of the thermoscope. Without insisting on an explanation of 
the mode of action of the cause which is supposed to produce 
this effect, (which I might certainly do, as the supposition is 
perfectly gratuitous,) I will content myself with just observing, 
that as the surface of the opposite disk was also blackened, this 
supposed augmentation of the quantity of caloric emitted by the 
ball of the thermoscope, occasioned- by the blackening, of the sur- 
faces of the bodies presented to it, can be of no use in explaining 
the phenomena in question. 
The results of the two last mentioned experiments appear to 
me to be very important ; and I do not see how they can be re- 
conciled with the opinions , of modern chemists, respecting the 
nature of heat. 
In order to simplify our speculations on this abstruse subject, 
we have hitherto supposed, that difference of temperature depends 
solely on the difference of the times of the vibrations of the com- 
ponent particles of bodies. It is possible, however, and even 
probable, that it depends principally on the velocities of those 
particles : for it is easy to perceive, that the more rapid the 
motions of those particles are, the greater their elongations must. 
