ast. 
: 
148 Dr. Hare on the Cause of Heat. 
be useless, and the particles would in effect, possess the pre- 
dominant property alone, whether attraction or repulsion. 
If the properties were equal in power, they would annihilate 
each other, and the matter would be, as if void of either 
property. There must, therefore, be a matter, in which the 
self-repellent power resides, as well asgnatter in which at- 
traction resides. 
There must also be as many kinds of matter, as there are 
kinds of repulsion, of which the affinities, means of produc- 
tion, or laws of communication are different. Hence I do 
firmly believe in the existence of material fluids, severally 
producing the phenomena of heat, light and electricity. 
Substances, endowed with attraction, make themselves 
known to us, by that species of this power, which we call 
gravitation, by which they are drawn towards the earth, 
and are therefore heavy and ponderable ; by their resistance 
to our bodies, producing the sensation of feeling or touch ; 
and by the vibrations or movements in other matter, affect- 
ing the ear with sounds, and the eye by a modified reflection 
of light. Where we perceive none of these usual concomi-+ 
tants of matter, we are prone to infer its absence. Hence 
ignorant people have no idea of air, except in the state of 
wind ; and when even in a quiescent state designate it by 
this word. But that the principles, the existence of which 
has been demonstrated, should not be thus perceived, 1s far 
from being a reason for doubting their existence. A very 
slight attention to their qualities will make it evident, that 
they could not produce any of the effects, by which the ex- 
istence of matter in its ordinary form is recognized. ‘The 
self-repellent property renders it impossible that they should 
resist penetration; their deficiency of weight, renders their 
movements nugatory. When in combination, they are not 
perceived, but the bodies with which they combine ; and it 
is only by the changes they produce in such bodies, or their 
effects upon our nerves, that they can be detected. 
