264 Of Salts in Mineral Waters. 
Corners left triangular : (See Fig, XI. XL) 
whereas the Salts of our Inland Springs 
have all their Corners fharp and perfed:, as 
Fig. VI., 
Nitre , or Salt Petre , throws itfelf into 
long {lender fexangular Cryffals, whofe Sides 
are Parallelograms. One End conftantly 
terminates either in a pyramid-like Point, or 
elfe in a fharp Edge, according to the Pofi- 
tion of the Sides of two unequal Planes. 
The other End is always rough, and appears 
as if broken. Fig. VIE VII. 
The moft general, tho’ lead; noted of all 
the fojjile Salts among us, is a Kind of Wall 
or calcar ions Nitre, or Lime-fait, which 
may be collected from the Mortar of ancient 
Walls ; and is, as Dr. Lister fuppofes,- 
what a great Part of the Earth and Moun¬ 
tains confift of *. Its Cryftals are {lender and 
long, the Sides of them four unequal Paral¬ 
lelograms: their Point at one End is formed 
of two Planes with triangular Sides ; the 
other End terminates in two quadrangular 
* We are well allured, that in France it is the common Prac¬ 
tice for thofe who have the Superintendency of the King’s 
Salt~Petre Works, to amafs vaft Quantities of the Mortar and 
Rubbifh taken from old Buildings: whence, by proper Ma¬ 
nagement, they extract Abundance of this caicarious Nitre . 
And when they have got all they can from it, by letting it lie 
together for fome Years, it becomes impregnated anew, and 
affords alrnoft as much as it did at firft. 
* Planes; 
