Chemical Geology. 113 
furnace. Upon opening the barrel, the chalk was found converted into a 
compact, light bluish-white coherent mass, slightly lustrous on the frac- 
ture, and with cracks running through the whole. e surface was 
covered with a snow-white, earthy, well defined crust and the cracks were 
lined with white earthy particles, these, as well as the crust, were com- 
posed of caustic lime. The compact mass, however, on examination proved 
to unchanged in chemical properties, and its physical properties, 
The experiment repeated with fragments of rhombohedral eale-spar 
was also interrupted by the rupture of the gun-barrel. The smaller 
ered to be erystalline marble. 
Notwithstanding the frequency with which this experiment of Hall's 
has been quoted, and the use that has been made of it not only in ex- 
Plaining geological phenomena, but in serving as the foundation of whole 
theories, it was never repeated{ or confirmed and the experiments of the 
th : 
sidered as due to heat alone, they were manifestly assisted by 
agencies, a conclusion also arrived at by Bischof, although in a different 
manner.— Pogg. Ann., cxi, 156. G. J. B. 
t Gehlen: Journ. f. Chem. u. Phys. i, 271. : :. i 
t Bucholz made se Lectin As. 3 incidentally in the epee of caustic lime 
from chalk, which in the experiment had not been entirely burned. 
Am. Jour. Sc1.—Sxconp Series, Vor. XXXII, No. M4.—JuLr, 1861. 
15 
