On Sal JSJitnim and Nitro-A'erial Spirit 33 



principally produced in such soil as is imbued with 

 saline - sulphureous particles — as, for instance, in 

 slaughter-houses, stalls, stables, and the like. In fact, 

 fixed or volatile salts provide suitable material for the 

 production of nitre, but sulphureous particles con- 

 tribute in no other way to the generation of nitre 

 than by exciting, when they effervesce with nitro- 

 aerial particles, that heat in the earth's bosom by 

 which first nitrous spirit is produced and then nitre 

 itself. For, as has been shown above, the sul- 

 phureous particles of terrestrial matter must not be 

 supposed to constitute nitre in part. 



It is in some measure established I think from what 

 has been said what the elements are of which sal 

 nitrum is composed. For it seems to consist of salt 

 of three kinds, of which one, the most active, is derived 

 from the air, and it has an ethereal and fiery nature. 

 This salt, as an architect, forges for itself from terres- 

 trial matter a saline vehicle in which, as in a fitting 

 subject, it resides. The saline vehicle along with the 

 fiery salt which occupies it forms the spirit of nitre, 

 which from the moment of its production meets the 

 fixed salts of the earth which have attained to proper 

 maturity, and coalesces with them to form common 

 nitre. So much then for sal nitrum. 



