80 
The experiments of Professor Graham in 1867, and more 
recently those of Mr. Parry, show that hydrogen, carbonic 
oxide and carbonic acid, and nitrogen are evolved from 
wrought iron, cast iron, and steel, when heated in vacuo. 
Therefore it seems probable that a part of the hydrogen 
produced by the action of the acid on the iron may be 
absorbed by the iron, its nascent state facilitating this. 
And when the iron is heated by the effort of breaking it, 
the gas may bubble up through the moisture on the frac- 
ture. 
In Mr. Parry’s experiments while one vol. of iron evolved 
two vols. of gas when heated strongly in vacuo ; one vol. of 
mild steel evolved only T3 of a vol. of gas. If from a small 
evolution of gas during heating of steel in vacuo we may 
argue a very small evolution of gas in steel soaked in acid, 
then we are led to suppose that the bubbles evolved from 
the hot moist fracture of a piece of steel will be very small 
or imperceptible, which experiments amply confirm. 
