Of Salts . 315 
evaporated until a little film appears upon it, runs into 
cryftal. Diflolution and filtration are made ufe of, that 
the falts may be purged from all drofs ; otherwife if any 
foreign matter fhould get in, not only the tranfparency 
of the cryftals would be impaired, but their figure alfo 
would be mangled and broken. 
Of the figures of falts. 
I T is generally agreed, that all bodies have their falts, 
which produce many furprifing changes, by their dif¬ 
ferent configurations and impreflions, both in folids and 
fluids, in things animate and inanimate. As to the figures 
of them, they are obvious to every beholder; their beauty 
and variety are fo admirable, that fcarce any thing in na¬ 
ture can entertain the eye more agreeably than thefe do, 
when it is aflifted with a good microfcope. 
In common fait, we plainly difcover quadrilateral 
pyramids with fquare bafes. In fugar, the fame pyramids 
with oblong and rectangular bafes. In allum, they rife 
with fix fides, fupported with an hexagonal bafe. The 
cryftals of vitriols, referable icicles, united one to another 
with great variety, among which lie fome polygons. Sal- 
armoniac very elegantly imitates the branches of a tree; 
and hart’s-horn looks like a quiver of arrows; Glauber’s 
fal mirabilis, which is made of common fait and vitriol, 
exhibits the figure of both falts. Nitre appears in certain 
prifmatic columns, not much unlike bundles of flicks; 
among which there are interfperfed fome of a rhomboidal, 
and pentagonal figure, which feem to come very near 
thofe of common fait. Hence Lemery very juftly re¬ 
marked, that nitre could not be purified by any art or 
contrivance whatfoever, but fomething of a fal gem, or 
foffil 
