PHILOS0 P H10 A L 
BA N S A C T I O N 
OF THE 
ROYAL SOCIETY 
OF 
LONDON. 
FOR THE YEAR MDCCCLXXXI. 
VOL. 172.—PART I. 
LONDON: 
PRINTED BY HARRISON AND SONS, ST. MARTIN’S LANE, W.('., 
fgriirters in Orbinarg to Per Hlajestg. 
MDCCCLXXXI. 
