Chap.$. concerning A I R^ &'c. 149 



This both fhews the ill Tendency of Ex- 

 tremes in Aerial Subftances, and that without 

 a temperate Air all things are in Confufion ^ 

 and the truth is, could we fpare any of the 

 Agents Providence has appointed in the bufi- 

 nefs of Vegetation, this of Air could be the 

 leaft 5 we could certainly better fpare the Ab- 

 fence, or at leaft the immoderate Strength of 

 the Sun, than this: Sure I am, if we were 

 to have no Air, Nature would foon breathe 

 her laft. 



I would therefore, from what I have been ^^^^ ^-^w/^ 

 laying down, eftablifli this as a Principle, J^^^J^'"^'"' 

 That there is in Nature always two Oppofite 

 Principles that occajion Agitation, and in this 

 cafe Fermentation 5 and in this it is, firjl, the 

 Sap which is liquid, and, fecondly, the Air 

 perfpiring through the Pores of the Earth and 

 all Plants, and infmuating itfelf into the Sub- 

 fiance of the Sap, that is the firft Caufe of 

 this Fer?nent, efpecially when agitated by the 

 additional Power of the Sun. And this in- 

 deed is the firft Principle or Motion of 

 Growth, in which Air is a very great Co- 

 efficient ; And if this be well underftood, 

 the fucceeding Accounts of the Rife and 

 Afcenfion of Sap in Trees, and, in fhort, 

 the whole Scheme of Vegetation will eafily 

 be accounted for. 



But to be more particular in the Operation 

 of Air upon the Earth, and to omit any more 

 Parallels thereon. 



L 3 Befides 



