[ xxvi ] 



" not grow and thrive, as they did 

 " molt remarkably in my firft ex- 

 " periments at Leeds, the reafon of 

 u which I cannot difcover. — In 

 " thole inftances in which the plants 

 " grew the heft, they were, how- 

 " ever, but fickly, as appeared by the 

 ik leaves foon turning yellow, and 

 u falling off when the leaff motion 

 u was given to them. In fome 

 a cafes, however, as in thole men- 

 u tioned in vol. I. p. 91, I faw no 

 u particular reafon why the air 

 ii iliould not have been meliorated. 

 a Upon the whole, I ftill think 

 '* it probable, that the vegetation 

 " of healthy plants, growing in fi- 

 " tuations natural to them, has a 

 i6 falutary effect on the air in which 

 " they grow. Fpr one clear in- 

 u fiance of the melioration of air in 

 ** thefe circumftances iliould weigh 



" againit 



