122 Professor Adams on the. Theory of the Thermometer. 
for as they can neither see, nor touch, nor weigh. calorie, 
they are obliged to strip it, at least-as far as our senses are 
concerned, of all the most apparent properties by which we 
are assured of the existence of matter; such as extension, 
impenetrability, and gravity. This opinion, is supported 
by considerable evidence, though perhaps. not sufficient to 
give entire satisfaction. git 
Other philosophers, refer the phenomena of heat to a vi- 
bratory motion of the particles of matter, varying in veloci- 
ty with the perceived intensity of the heat. In fluids and 
gases, the particles are conceived to have a motion round 
their own axes.. Temperature, therefore, with them, will 
increase with the velocity of the vibrations, and increase of 
capacity will be produced by the motion being performed 
in greater space. The loss of temperature, during the 
change of solids into liquids and gases, will depend upon 
loss of vibratory motion, in consequence of the acquired 
rotary motion.* The most distinguished advocate of this 
hypothesis, of late years, is Sir H. Davy. A detailed ac- 
count of his views may be found in his ‘ Elements. of 
Chemistry.” Since, in the exact sciences, the opinion of 
no man is better than the reasons which he gives for it; 
with perfect respect for the talents. of this illustrious chem- 
ist, and with the greatest admiration of his splendid discoy- — 
eries, it is probable, that his hypothesis will never. be ex- 
tensively received. Indeed, the. idea, that all the facts 
with which we are acquainted respecting heat, can be made 
to depend on motion of any kind, is perhaps scarcely less. 
than inconceivable. It is difficult, to understand, how this 
hypothesis can be plausibly supported. A highly ingen- 
ious and convincing argument against it, of the nature 
of a-reductio ad absurdum, has. been constructed. by: 
Dr. Have, and will doubtless be recollected by the readers 
of this journal.f . 2 ‘idehocen 
Another class of philosophers, attaching themselves to 
neither of these hypotheses, limit themselves to admitting 
the facts-common to both, and consider the term caloric, 
as the name of a cause whose nature is not known any 
further than, that it gives us the sensation of heat, and pro- 
duces peculiar effects upon the substances around us. - 
* Brande, Manual of Chem. 1. 248. 
+ Vol. IV, 142. 
