Nitre what, and how obtained . 67 
part of a Column with Hairs palling thro* 
its Perforations. 
This Salt is found juft under the Turf 
about Patnefs in the Northern Parts of the 
Kingdom of Bengal, and probably in other 
Places thereabouts, whence it is brought 
to us in great Abundance by the Eajl - 
India Company * : but all produced in Europe 
appears either like a kind of Efftorefcence 
adhering to Rocks and Walls, being what 
the Ancients called Aphronitum, and what 
is called by us Natural Salt-Petre, of which 
the Quantity collected is but fmall; or is 
elfe extracted by Art from certain Earths 
and Stones, the Ruins of old Buildings, 
the Dung of Pigeons, and the Excrements 
and Urine of other Animals : the Man¬ 
ner of doing which is related by feveral 
Authors. 
Examin’d chemically (and to ufe the Che- 
mift’s Terms) it appears compounded of a 
volatile acid Spirit, and a fixt alkalious Salt. 
Such a Spirit the Air abounds with: and 
this Spirit by penetrating into, and becom¬ 
ing incorporated and fixt by the alkali¬ 
ous Salts of Lime, and fome Sorts of Earth 
and Stone, is probably the active Principle 
that produces Salt-Petre . It is alfo very 
likely owing to the fame Principle, that Salt- 
* Vid. Woodward's Method of FoJJtls, p. 36. 
F 2 
Petre 
