Seel. II. Agriculture and Vegetation. 133 



acids, thefe bodies will draw it out, and be 

 converted to a neutral faline fubftance, en- 

 joying the properties of fait, fuch as folu- 

 bility in water, difTolving oils, and render- 

 ing them mifcible with water. Nothing, 

 then, remains to be proved, in order to the 

 converfion of thefe manures into a fait, 

 but that the air contains an acid fait. 



THIS has been the opinion of the greateft 

 chymifts, not from theory alone, but be- 

 caufe they difcovered, that alkaline falts, 

 when expofed to the air, were converted 

 into neutral onesj and that metals, fuch 

 as tin, copper, and lead, were corroded, 

 and converted to a fait. Whether there is 

 fuch a fait, and what its nature, will be 

 beft afcertained and illuftrated, by confider- 

 ing the manufacture of nitre. This procefs 

 ' too will (how the operation of the different 

 manures, as thefe are the very materials 

 ufed in this manufacture. 



K 7 THE 



* w 



