water, and over that fpread themfelves in an ice, it may 
be as probable, that by the greater heat of the Sun, the 
Nitre of Latron is feparated from the water after the 
fame manner : And as .in the evaporation of other mine- 
ral waters, when the water is not ftrong enough to hold 
up the Salt, it is generally covered with a thin film ; fo 
I luppofe in evaporation of the Natron, fome parts of the 
water being flown away, the particles of the Sal Marine 
branch one into another, and foincruftate upon the fur- 
face of the water. 
In this Hypothecs lw2iS the further confirm'd, by this 
E^^periment, I cook fome of t\it Natron anddilTolved it 
in water, and fet it to evaporate, and I found that the 
Salt did not incruftate upon the water till B parts of the 
water was evaporated, it did not therefore feem proba- 
ble that the Nitre came all from the bottom to the top,: 
and fo condenfed by the heat of the Sun, but that they 
incruftated when the faline particles brancht one into a- 
nother, fome of the aqueous parts being exhal d. 
Thereafon why its volatile AJkaly in evaporation does 
not fly quite away, is becaufe it is held there by the Sal 
Marine. 
The next thing to be confidered is its ule in Phyfick : 
By Pliny it's commended in Ulcers, Inflammations, Pal- 
fey in the tongue, Confumptions, CoUick, Hemorha- 
ges. Purulent ears, and intermitting Fevers. By 
Gallen it's fa id, deficcat^ac digerity multo autem majus e- 
jus ^uma. 
By Agricola it's prefcribed in the fame cafes, commend- 
ed as a Cephalic. Of wonderful fuccefs in the griping of 
the Guts, intermitting Fevers and the Leprofie. Mathi-* 
olus commends it in the fame cafes. 
By Hippocrates it is commended when the Menfirua are 
obftruded, and again (f^ith he) p^rgat humor es alios, 
convenit in al ortionibus ubipuer baud exierit, he likewife 
commends it in fome kind of barrennefs, and to this Kir- 
