166 Count Rumford’s Enquiry concerning the Nature of Heat , 
analogies between the rays of light and those invisible rays 
which all bodies, at all temperatures, appear to emit, that we 
can hardly doubt of their motions being regulated by the same 
laws. 
Perhaps there may be no other difference between them, than 
exists between those vibrations in the air which are audible, and 
those which make no sensible impression on our organs of 
hearing. 
If the ear were so constructed that we could hear all the 
motions which take place in the air, we should, no doubt, be 
stunned with the noise ; and, if our eyes were so constructed as 
to see all the rays which are emitted continually, by day and 
by night, by the bodies which surround us, we should be dazzled 
and confounded by that insupportable flood of light, poured in 
upon us on every side. 
Taking it for granted that these invisible radiations exist, we 
will endeavour to trace the effects which must necessarily be 
produced by them, in order to see if these investigations will not 
lead us to a discovery of the causes of some appearances which 
have hitherto been enveloped in much obscurity. 
Suppose two concave reflecting mirrors, of highly polished 
metal, each 18 inches in diameter, and 18 inches focal distance, 
to be placed opposite to each other, at the distance of 10 feet, in 
a large quiet room, in which the air, and the walls of the room, 
remain constantly at the same temperature, (that of freezing 
water, for instance,) without any variation. 
If we suppose the floor, ceiling, walls of the room, and doors 
and windows, to be lined with a covering of ice, at the tempera- 
ture of freezing water, we can then, without any difficulty, con- 
ceive that the temperature of the room may remain the same, 
