Rocky Spring , and Sea-Salt. 51 
thofe two Figures N° II. and Spring-Salt 
with thofe at N° III. 
Mc-ft Writers reprefent the Crydals of 
thefe Salts as Cubes ; and fuch in Truth 
they feem originally to be : I mean, when 
fo minute as jud to become didinguiihable 
by the greated Magnifier : large Maffes of 
Sal-Gem , and fometimes of Sea and Spring- 
Salt, are feen in cubical or rectangular 
Figures, made up without doubt of innu¬ 
merable minute Cubes. But in all Exami¬ 
nations by the Microfcope of the Solutions 
of thefe Salts, the Bodies that form and 
grow under the Eye are, in the general, 
not Cubes, but hollow Pyramids : though a 
Prepodefiion that the Cry dais of fuch Salts 
are Cubes, makes thefe Figures, even under 
InfpeCtion, often imagined fo to be: for 
the fquare Out-line, which is only the Safe 
of an hollow Pyramid (if great Attention 
be not employed) is apt to give the Idea of 
a Cube: and the diderent Ranges or Steps, 
which by a gradual Diminution upwards 
compofe the Hoping Sides of the Pyramid, 
are eadly midaken, from their great Trans¬ 
parency, to be no other than Lines upon 
the Surface of the Cube. Indeed a few 
Cubes are feen now and then amongd the 
other Forms, but their Number is far too 
fmall to conclude the general Figure from ; 
thofe very Cubes in feme Politions have 
E 2 likewife 
