PHILOSOPHICAL 
TRANSACTIONS 
OF THE 
ROYAL SOCIETY 
OF 
LONDON. 
FOR THE YEAR MDCCCLXXXI. 
VOL. 172. 
LONDON: 
PRINTED BY HARRISON AND SONS, ST. MARTIN’S LANE, W.C., 
printers in Orbinarn to Her Hlajcstg. 
MDCCCLXXXU. 
