cf Magneftan Earth. 46 r 
To the evidence adduced by Dr. Wall, in his 
ingenious paper, on the origin of the Fixed Vege¬ 
table Alkali, and of Nitre, I have to add that of 
Baron Dillon, the intelligent tranfiator of Mr.- 
Bowles’s Travels in Spain, who has, perfonally, 
allured me of the authenticity of the fad; and 
of a Gentleman who refided, during feveral 
years, in the Eafb Indies, as fuperintendent of 
the manufactures of the Company, and fully 
confirms the account, that Nitre is procured, 
from the foil of certain places in that country, 
merely by lixiviating it, and evaporating the 
water, without the addition of any alkaline fait. 
The Duke de Rouchefoucauld alfo obtained one 
ounce of nitre in the pound, from chalk of 
Roche Guyon : and it is faid, by M. Fourcroy, 
to be found quite pure in chalk beds. 
Indeed the relation between the production 
of thefe two falts is very ftriking ; for at the fame 
time that Nitre is formed in the beds, a con¬ 
siderable quantity of Common Salt feems to be 
produced ; and, during the evaporation of the ni¬ 
trous ley, fuch quantities of it are feparated, that 
we cannot fuppofe the whole to have pre-exifted, 
as fuch, in the urine and other animal matters, 
ufed in the nitre heaps, but mud regard it, in 
fome meafure, as a new produft. 
Nor does the analogy Hop here. Together 
with the Nitre, which is formed in the beds, 
and with the Sea-Salt, which we fuppofe to be 
formed 
