PHILOSOPHIC A L 
TRANSACTIONS, 
OF THE 
ROYAL SOCIETY 
O F 
LONDON. 
VOL. LXX'. For the Year 178©. 
PART II. 
LONDON, 
SOLD BY LOCKYER DAVIS, AND PETER ElMSLlfy 
PRINTERS TO THE ROYAL SOCIETY. 
MDCGLXXXI, 
