150 he Principles of Part III. 



vifible, in proportion to their ftrength of 

 attracting acids. This happens really fo 

 in fact, and is a fhong confirmation of the 

 truth of our reafoning : for afhes have the 

 ipeedicft effects of any manure j becaufe 

 the alkaline falts which they contain attract 

 acids Wronger than any body. Soot and 

 dung come next, which are volatile alka- 

 lines, whofe attraction comes next to the 

 firft; then the clafs of abforbent earths. 

 The fame obfervation is made of the marls ; 

 for, according to their rank as attracters 

 of acids, fo they operate on ground j firft 

 fhell, next clay, and laft of all ftone marl ; 

 which will fometimes continue in the 

 ground four or five years before it ihow 

 any effects. The fame turn all thefe ma- 

 nures keep in lofing their effects ; for the 

 fooneft converted to fait muft be the fooneft 

 exhaufled. 



AN objection will naturally occur to every 

 one againft this opinion, though fupported 

 by the greateft Strength of experiment i 



which 



