PHILOSOPHICAL 
TRANSACTIONS 
OF THE 
EOYAL SOCIETY 
OP 
LONDON. 
(B.) 
FOE THE YEAR MDCCCXC. 
VOL. 181 . 
FEINTED BY HAEEISON AND SONS, ST. MAETIN’s LANE, W.C., 
prmErs xtt #r!bmarg to '§n piajfstg. 
MDCCCXCI. 
