PHILOSOPHICAL 
TRANSACTIONS 
OP THE 
ROYAL SOCIETY 
OF 
LONDON. 
(B.) 
FOR THE YEAR MDCCCXC. 
VOL. 181 . 
LOHD OH: 
PRINTED BY HARRISON AND SONS, ST. MARTIN’s LANE, W.C., 
^rijtRrs in ©rbinarg to ''§i:x l^iajfstii. 
MDCCCXCI. 
