[ xl ] 



the leaves depends upon too many 

 cir.cum fiances to he conflantly of 

 the fame quality. Some more or 

 lefs light of the fan thrown upon 

 the jar will make fome difference; 

 the leaves heing more or lefs crowded 

 together, will make a remarkable 

 difference, as a great number of 

 them may be fhaded from the fun 

 by otheis. 



As I made the greater! part of 

 my experiments according to the 

 prefent method of proceeding of 

 my refpeclable friend the Abbe 

 Fontana, it would have been diffi- 

 cult to imitate the experiments re- 

 lated in this work, and even to 

 pnderitand the manner in which 

 they were made, if he had not 

 given me leave to anticipate the 

 publication of his own ingenious 

 contrivance, and of his prefent me° 



thocl 



