168 THE COMMON METHOD BY HEAT. 
and beneath it when it cracks open. ‘This crust is of a 
very different kind from that which is formed when too 
much lime is used, and is more abundant and difficult to 
get rid of. 
In the production of sugar, the common mode of treat- 
ment is never in the least successful, except when the canes 
have been selected, the juice naturally very pure, and the 
quantity of acid and albuminous matter which it contains 
is extremely minute. 
