SOILS, MANURES, &c. 253 
ftrongly alkalefcent than the fouthern and 
eaftern coafts : this phenomenon appears 
to be an objefl worthy of philofophical 
inveftigation. 
It is obferved by chymifts, that the 
caufticity of falts depends on the ab- 
fence of fixed air; which perhaps might 
be more intelligibly denominated the 
nitrous or aerial acid, becaufe it is 
reafonable to conclude, that the acid 
being, when heated, exceedingly more 
volatile than the alkali, becomes expelled 
and driven off in the procefs of incinera¬ 
tion, and that until the alkali has reco- 
* 
vered its acid, it remains in a flate of 
caufticity ; but upon a fufficient expofure 
to the atmofphere, it will regain its acid, 
and become mild or effete ; therefore it 
cannot be doubted that the abfence of the 
aerial acid is the foie caufe of caufticity. 
The 
