Cryjlals of Nitre. 
cut off more obliquely* and compofing 
an hexangular Plane. The Sides of 
this Column are four broader and two 
narrower Planes, whereas the prece¬ 
ding confided of two broader and four 
narrower. 
g. Another Cryffal, having one End a great 
deal Hoping and graduated, and the 
other cut off at different Angles. 
4. A Cryftal indofed feemingly within ano¬ 
ther, and forcing its way out, by burff- 
ing through the other’s Side. 
5. A Column with fix equal or nearly equal 
Sides: one End broken, and the other 
forming an hexangular Pyramid, whofe 
Sides are correfpondent to thofe of the 
Column. 
6. A fhort hexangular equilateral Column, 
both whofe Ends are Pyramids, having 
Sides that correfpond with thofe of the 
Column. 
One Particularity in Nitre is, that its 
Cryftals are perforated from End to End 
all along, juff within the Corners where the 
Planes interfed; as may be proved in the 
larger Shoots, by the Breath’s pafling thro* 
them eafiiy or> blowing. Thefe Channels 
are pointed out in Figure 2, by the fix 
Dots at its End $ they are likewife fiiewn 
s^iore perfedly at Fig. 7. which reprefents 
* GuglisL Difc- fcpra Is Fig . de Sa!i s p. i z. 
pari. 
