9 NITRE. 471 



7. SOURCES OF NITRATE OF POTASSA. 



(a.) Tliere are some soils which contain so much of it that they are 

 catted saltpetre grounds. In Italy and Spain, and in the latter es- 

 pecially, it is found, even in the dust of the roads ; and when the 

 crops of wheat fail, the farmers frequently obtain an indemnity, by 

 lixiviating the soil for nitre.* In India, in China, and in the eastern 

 parts of Persia, saltpetre earths are very common, and the salt even 

 effloresces on the surface ; and from these countries a great part 

 of the nitre used in Great Britain and America is brought. It is 

 found in pasture grounds, near Lima, in South America, and in 

 Podolia, a province of Poland, in little hillocks, being the ruins of 

 habitations, in a plain country, formerly populous. 



(b.) Nitre is usually found in places where there has been an accu- 

 mulation of animal and vegetable matters, or an abundance of animal 

 effluvia, having free communication with the air, and with alkalies or 

 lime ; as in the ruins of old houses, in the earth of cellars, and sta- 

 bles, and in pigeon lofts, in which places it often effloresces, pro- 

 vided the walls be of lime, and in general in low situations, which 

 have been frequently impregnated with animal or vegetable fluids in 

 a putrescent state. Nitre is produced in grounds much trodden by 

 cattle, and frequently impregnated with their excrements. Ure. In 

 such places the nitre is constantly reproduced, after being remov- 

 ed, especially if the place have a northern exposure. In France 

 the richest part of the vegetable mould is often found to contain nitre,f 

 and in this country, such sources were resorted to, to afford nitre 

 during the war of the revolution. The earthy floors of the tobacco 

 houses were found to be particularly rich in this salt. 



(c.) Nitre is also found in marly and calcareous grounds ; or rather 

 another salt is found in such places, greatly resembling nitre, and into 

 which it is easily con verted. J 



(d.) In the calcareous caverns of the Western and South Western 

 States of the United States of America, there are vast resources for 

 manufacturing nitre, derived from the nitrate of lime, found in these 

 caves. It is changed into saltpetre by wood ashes one bushel of 

 earth, in some instances, yielding from 3 to 10 pounds of the salt. 

 In Kentucky, there are masses of ready formed nitre, mixed in sand- 

 stone rocks. 



(e.) In vegetables. Nitre is found in borage, bugloss, parietaria, 

 hemlock, and the sunflower ; and in the dried branches of this last, 



* Black, Vol. II, p. 444. 



t They prefer the earths that are at a little distance from the surface of the 

 ground ; they are distinguished by their sharp taste ; it is a rich nitre ground that 

 contains 5 per cent. 



t The wells of great cities also afford this salt. In Peale's Museum, in Philadel- 

 phia, is deposited a quantity of nitre, obtained along with other salts, during the 

 analysis of the pump water of that city. 



