PHILOSOPHICAL 
n i 
TRANSACTIONS, 
OF THE 
ROYAL SOCIETY 
4* 7 
O F 
LONDON. 
r 
VOL. LXXXI. For the Year 1791. 
PART I. 
LONDON, 
SOLD BY PETER ELM SLY, 
PRINTER TO THE ROYAL SOCIETY. 
MDCCXCI. 
