Dr, Rujh on the Progrejs^ &c. 183 



neceflary to employ concave ones, and to pro- 

 cure them ftill more fo, the older he grew. 

 This change in his fight, he informed me, he 

 firft obferved, after having for fome time, 

 accuftomed himfelf to read a book, printed in 

 a fmall charader, and, that, frequently in the 

 clofe of the evening, when the light was not 

 favourable for the purpofe. 



As this is an uncommon faft, and may ferve 

 to confirm the propriety of the dodrine, I have 

 alluded to, I thought it might be proper to 

 communicate it to the Society. 



Jn Account of the Progress of Population, 

 Agriculture, Manners, and Government 

 w Pensylvania. In a Letter from Ben j amiv! 

 Rush, M, D. and Profejfor of Chemijiry in the 

 Univerfity of Pensylvania, to Thomas Per- 

 civAL, M. D. F. R. S. ^c. &c. 



READ DECEMBER 6, I786. 



SIR, 



WHATEVER tends to unfold fafts in the 

 hiftory of the human fpecies mult be in- 

 terefting to a curious inquirer. The manner of 

 fettling a new country exhibits a view of the hu- 

 man mind fo foreign to the views of it which 

 N 4 have 



