Spheroidal State of Bodies—Proof by Fire. 109 
consists of pouring a mass of melted glass into a pail of 
water, and kneading it, though red-hot, with the hands. 
In this experiment there are two periods well marked,— 
in the first, the mass of glass is insulated in the midst of the 
water ; in the second, it is covered with a solid and trans- 
parent layer, which allows us to see the incandescent mass. 
The duration of the first period is very short, and it is only 
during the second that the melted glass can be kneaded with 
impunity. This experiment, M. Dumas added, has been 
known from time immemorial ; it has been noticed by Bel- 
lani, who remarks, that the mass of glass produces no biss- 
ing or sign of ebullition in the water, /a guale acqua rimane 
tranquilla come ponendovi un pezzo di ghiaccio.* 
Let us now try to find the rationale of these facts. 
We have the formula m c ¢, which gives the quantity of 
heat contained in any body. 
Let m be the mass, expressed in kilogrammes ; 
e the specific heat of the body ; 
t its temperature. 
But here we must abstract the facteur m, because there 
was no contact between the hand and the melted metal, and 
because the experiment presents no difference whether made 
with 10 kilogrammes or 1000. The sensation experienced is 
the same in either case, and it may be easily understood, know- 
ing the repulsive force of the red-hot surfaces which are opposed 
to the contact of any body. 
The finger or hand is, therefore, insulated in the middle of 
the melted mass, and thus preserved from the disorganising 
action of the burning matter. I repeat, that we must ab- 
stract the mass. 
Let the two facteurs ctremain. I shall suppose, and 
it is a sufficient approximation, that the value of c=0°15, 
and that of <=1500°, the temperature of the melted matter ; 
now the product of 1500° x 0:15= 225. 
It thus appears that the skin of the experimenter will be 
exposed only to 225 calorics. This certainly is a consider- 
* Giornale di fisica di Pavia, anno 1816, P. 225, 
