202 ESSAYS anp OBSERVATIONS 
folution of alum in this, that they give a 
red colour to the infaGon of turnfol. ; 
NEITHER this earth, nor that of ani- 
mal bones, can be converted into quick- 
lime by the ftrongeft fire, nor do they fuf- 
fer any change worth notice. Both of 
them feem to attract acids but weakly, 
and to alter their properties lefs when u= 
nited to them than the other abforbents. 
2 gh cn Ot wate 
La reflecting afterwards upon thefe ex= 
periments, an explication of the na= 
ture of lime offered itfelf, which feemed 
to account, im an eafy manner, for moft. 
of the properties of that fubftance. 
Ir is fufficiently clear, that the calcari- 
ous earths in their native ftate, and that 
the alkalis and magnefia in their ordina- 
ry condition, contain a large quantity of 
fixed air, and this air certainly adheres to 
them with confiderable force, fince a {trong 
fire is neceflary to feparate it from magne- 
fia, and the ftrongeft is not fufficient to 
| expell 
