88 M. POUILLET ON SOLAR HEAT, 
verts to the supposition that they are different in the two cases; 
but it must be remarked that all the experiments which can be 
made being relative to changes of heat in which these constants 
are destroyed, no observation can ever give their value. 
There remains therefore respecting this constant of emission 
a theoretical difficulty the more serious, because upon it alone 
depends the impossibility of considering the absolute emission 
and of assigning a value to the real and total quantities of heat 
which are emitted by the radiating surfaces. It appears to me, 
however, that this difficulty is not incapable of solution: the 
constant in question is only a product of the calculation ; it can- 
not represent any mechanical:condition nor any physical phee- 
nomenon, and its value must be null in all cases. 
Let us in fact suppose that e, or the total quantity of heat 
emitted by the unity of surface of a body during the unity of 
time, be represented by the known function of the temperature, 
plus a constant, so that we have 
e=B.f.a't’+ 0, 
and let us determine the laws of cooling, by supposing that the 
inclosure has a complete absorbing power, whilst the globe has 
only an absorbing power represented by J’. 
Let § be the temperature of the inclosure, e! the quantity of 
heat which it emits from the unity of surface in the unity of 
time, and 1 its emissive power: the total quantity of heat lost 
by the globe will be 
ess 
the quantity of heat emitted from the unity of surface of the in- 
closure being é’, the portion which reaches the globe is always 
e’ sin? w; 
the globe only absorbs a portion 4’, consequently a quantity 
8! e' sin? w, 
and it absorbs together of that which it receives from the entire 
inclosure, 
Jb eésin?tw=sble; 
its definitive loss is therefore 
es—slb'ed. 
But if we have 
e=Bf.a't'+C, e =B.a'+C, 
this loss of heat becomes 
sBf(a't*— a’) +sC—/), 
because the radiating power f of the globe is equal to its ab- 
sorbing power J. 
