[ xxiii ] 

 to -r^dth of the two airs employed 

 in the experiment. 



The difcovery of Dr. Prieftley, 

 that plants thrive better in foul air 

 than in common and in dephlogifti- 

 cated air, and that plants have a 

 power of correcting bad air, has 

 thrown a new and important light 

 upon the arrangement of this world. 

 It fhews, even to a demonftration, 

 that the vegetable kingdom is fub- 

 fervient to the animal; and, vice 

 verfd, that the air, fpoiled and ren- 

 dered noxious to animals by their 

 breathing in it, ferves to plants as a 

 kind of nourifhment. But in what 

 manner this faculty of the plants is 

 excited remained {till unknown. 



There was even fome doubt left 



in the mind of many philofophers, 



whether the facts related by Dr. 



Prieftley were not owing to fome 



b 4 par- 



