460 Mr. Henry on the Natural Hifiory , &c. 
difcovered, by an ingenious chemift,* that 
though Nitre is produced by the above fubftances, 
with the accefs of air, yet if they be fo placed 
that the air may be excluded, and the fituation 
perhaps not too moift, Sulphur, and not Nitre, 
is the refult. So that the three mineral acids 
ihould feem to have a fimilar origin, and it is not 
without good grounds, that they are faid to be 
modifications of each other. 
But it may be faid, that the analogy in the 
produ&ion of Sea-Salt and of Nitre is not corn- 
plete. That, in the one, both the alkaline and 
acid parts of the fait are formed; whereas, in the 
other, the acid only is produced in the beds, 
and it is necefiary to add an alkaline fait to 
conftitute the bafis of the Nitre. I cannot how¬ 
ever allow of the force of this obje&ion. Though 
the addition of the alkali be necefiary, in thele 
northern latitudes, yet, in warmer climates, 
where Nature is more vigorous and a&ive, there 
is no doubt but fhe forms, or devellopes, both 
the acid and alkali of Nitre, at the fame time. 
* M. Fougeroux. vide Memoirs del ’ Academie Royale 
des Sciences pour l’annee 1780. 
The Sulphur, produced under the above circumftances, 
was found, amidft the ruins of an old houfe which had 
been built in a very filthy place, contained in a mafs of 
earth, and, in part cryftallized; and conftituting, in 
feveral of the la.ge portions of the earth, a-third of the 
whole mafs. 
To 
