and the Mode of its Communication. 165 
that body, namely, those calorific rays which that hot body 
emits, and those other rays (which with regard to the sur- 
rounding bodies are neither calorific nor frigorific) which it 
reflects. 
On a cursory view of the subject, one might be led to imagine, 
that, as the rays which proceed from the hot metallic body are 
of two kinds, the energy of the calorific rays, which properly 
belong to the hot body, might be diminished by those other 
reflected rays by which they are accompanied, and with which 
they may be said to be mixed ; but, a more careful examination 
of the matter will show that this cannot be the case ; that is to 
say, as long as all the surrounding bodies continue to be at the 
same temperature. If the temperature of the surrounding bodies 
be different, such of them will be affected, by the reflected rays, 
as happen to be of a temperature different from that from which 
the ray originated ; but still, the effects produced by the rays 
emitted by the hot body, will be the same, or their power of 
effecting changes in the temperatures of other (hotter or colder) 
bodies, will remain undiminished, and unchanged. 
The reason why their effects are not more powerful than they 
are found to be, is not because they are mixed with other re- 
flected rays, but because they are few ; the greater part of the 
rays which the hot body actually emits being reflected, and 
turned back upon itself, by the reflecting surface by which it is 
immediately surrounded. 
That the reflecting surface at which the rays of light are 
turned back and reflected, which impinge against the polished 
surface of any solid or fluid body, is actually situated without the 
body , and even at some distance from it, has been proved by the 
most decisive experiments ; and there are so many striking 
