22 On the Serpentine Rocks of Hoboken, N. J. &c. 
in medicine, and imported largely into this country, could 
here be established 
In England it has been found profitable to manufacture 
this salt from the calcareous magnesian minerals. In this 
process, however, it becomes necessary to saturate the use- 
less and predominating portion of calcareous earth besides 
the magnesia, which in the serpentine of Hoboken, and 
probably that of Baltimore, is entirely obviated by the ab- 
sence of every soluble earth but the magnesian. 
In Salinelle, in the department of Gard in France, this 
salt is fabricated to advantage from an earth which consists 
in the 100 parts of Silex 45, magnesia 22, water 32, and a 
trace of iron 
From such minerals and particularly from a substance so 
pure, unusually productive, and uncontaminated as that of 
the serpentine in question, the sulphate might be obtained 
in a degree of purity altogeter superior to that of commerce, 
from the bittern of 
usually manufactured sea-water. which 
abounds in foreign in ients. 
A puly on similar to that witiel is ersployedhs re- 
rit psum for agricultural purposes is all that would be 
requisite in these serpentine rocks ; and as far as my ex- 
periments have extended in the small way, the solution of 
this mineral is more complete before than after ignition, at 
least when a moderate heat is employe 
Inthe vicinity of G bout eight miles fr n Phil- 
adelphia, a serpentine Sietinsber occurs $0 very similar to the 
Fahlunite of Sweden, that I could not satisfy myself of their 
distinction in any other way than by the educts of analysis, 
Like that mineral it occurs in disseminated, but partly con- 
fluent blackish-green masses, blended with a greyish-green, 
confusedly laminated tremolite, closely allied to Hornblende, 
and as weil as the serpentine, soft enough to be easily scrap- 
ed with a knife, and scarcely scratching glass. The frac- 
ture of this serpentine is somewhat conchoidal as in Fi ahlu- 
