108 On the Cause of Heat. 
can be no motion without matter. To surmount this difficulty, 
he calls up a suggestion of Newton’s, that the calorific vibrations 
of matter may send off radiant particles, which lose their own 
momentum in communicating vibrations to bodies remote from 
those whence they emanate. Thus, according to Sir Humphry, 
there is radiant matter producing heat, and radiant matter pro- 
ducing light. Now, the only serious objection made by him to 
the doctrine which considers heat as material, will apply equally 
against the existence of material calorific emanations. That the 
cannon, heated by friction in the noted experiment of Rumford, 
would have radiated as well as if heated in any other way, there 
can, J think, be no doubt; and as well zz vacuo, as the heat ex- 
cited by Sir Humphry in a similar situation. That its emission 
in this way would have been as inexhaustible as by the conducting 
process cannot be questioned. Why then is it not as easy to 
have an inexhaustible supply of heat as a material substance, as 
to have an inexhaustible supply of radiant matter, communicat- 
ing the vibrations in which he represents heat to consist ? 
We see the same matter, at different times, rendered self- 
attractive, or self-repellent ; now cohering in the solid form with 
great tenacity, and now flying apart with explosive violence in 
the state of vapour. Hence the existence, in nature, of two op- 
posite kinds of reaction, between particles, is self-evident. There 
can be no property without matter, in which it may be inherent. 
Nothing can have no property. The question then is, whether 
these opposite properties can belong to the same particles. Is it 
not evident, that the same particles cannot, at the same time, be 
self-repellent, and self-attractive ? Suppose them to be so, one 
of the two properties must predominate, and in that case we 
should not perceive the existence of the other, It would be use- 
Jess, and the particles would in effect possess the predominant 
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 as matter in which attraction resides. ho 
There must also be as many kinds of matter, as there are kinds 
of repulsion, of which the affinities, means of production, or laws 
of communication, are different. Hence I do firmly believe in 
the existence of material fluids, severally producing the pheno- 
mena 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 to- 
wards 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, 
affecting 
