the common principles of vegetation, carbon, hy- 
drogene, and oxygene. 
The alkaline sulphates and the earthy muriates 
are so seldom found in plants, or are found in such 
minute quantities, that it can never be an object 
to apply them to the soil. It was stated in the be- 
ginning of this Lecture, that the earthy and alkaline 
substances seem never to be formed in vegetation ; 
and there is every reason likewise to believe, that 
they are never decomposed; for after being ab- 
sorbed they are found in their ashes. 
The metallic bases of them cannot exist in con- 
tact with aqueous fluids ; and these metallic bases, 
like other metals, have not as yet been resolved 
into any other forms of matter by artificial pro- 
cesses ; they combine readily with other elements ; 
but they remain undestructible, and can be traced 
undiminished in quantity, through their diversified 
combinations. 
