150 Count Rumford's Enquiry concerning the Nature of Heat , 
These researches appear to me to be the more interesting, as 
I have long been of opinion, that it must be by experiments of 
this kind, (showing in what manner the temperature of bodies 
are affected reciprocally, at different degrees of temperature, and 
at different distances,) that the hypothesis of radiation must be 
established, or proved to be unfounded. 
When I speak of heat as being communicated to air imme- 
diately by a hot body which is cooled in it, I mean only, that it 
is not first communicated to other neighbouring bodies, and then 
given by them to the particles of air with which they happen to 
be in contact. In this last mentioned way, much of the heat, no 
doubt, which a hot body loses when cooled in air, is ultimately 
communicated to that fluid. 
I am far from supposing that the particles of air which, coming 
into contact with a hot body, are heated in consequence of that 
near approximation, receive heat in any other manner than that 
in which other bodies, at a greater distance, receive it. If, in the 
one case, it be generated, or excited, by the agency of calorific 
rays, or undulations, caused by the hot body, it must, I am 
persuaded, be excited in the same manner in the other. 
The reason why the particle of air which is in immediate 
contact with a hot body is heated, while other particles, near it, 
are not affected by the calorific rays from the hot body, which 
are continually passing by them, through the air, is, I conceive, 
because the particle heated is at the surface of the fluid, (air,) 
where these rays are either reflected, refracted, or absorbed; 
but, when a ray has once passed the surface of a transparent 
fluid, it proceeds straight forwards, without being farther affected 
by it, and consequently without affecting it, till it comes to the 
confines of the medium, or to the surface of some other body. 
