100 
Dr. Henry’s Analysis of several Varieties 
According to the proportion in which the earthy muriates 
are present in any kind of salt, will be its power of deliques- 
cence, or of attracting moisture from the atmosphere. It is 
not entirely, however, from the salts with earthy base, that 
common salt derives this quality ; for the most transparent 
specimens of rock salt, which I find to consist of absolutely 
pure muriate of soda, attract much moisture from a humid 
atmosphere. 
IV. The sulphate of magnesia and the sulphate of lime, both 
enter into the composition of all the varieties of salt prepared 
from sea water ; but the sulphate of lime alone is found in 
Cheshire salt. The proportion of sulphate of magnesia is 
greatest in that variety of sea salt, which has been formed by 
rapid evaporation. In foreign bay salt, its quantity is very 
insignificant. 
From the table it may be seen, that the proportion of sul- 
phate of lime is greater in foreign bay salt, than in any variety 
of British salt, even than in those which are prepared from 
sea water with a boiling heat. The only explanation of this 
fact, that occurs to me, is, that during the rapid evaporation of 
sea water, a considerable part of the calcareous sulphate is 
precipitated at an early stage of the process, and is partly re- 
moved in clearing the boiler, a process, which can scarcely be 
performed during the formation of bay salt, in pits whose 
sides are composed of moist clay. The remainder of the sele- 
nite, thus precipitated by the rapid evaporation of sea water, 
enters into the composition of the pan-scale. 
In the course of this inquiry, I was induced to repeat the 
same experiments several times, on various specimens of salt 
bearing the same designation ; and was surprised to find, that 
