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^ '' 
PHILOSOPHICAL TRANSACTIONS 
OF THE 
ROYAL SOCIETY OE LONDON. 
Series A, Vol. 220. TITLE, &c. 
TITLE, CONTENTS, INDEX, &0. 
A VOL. 220. 
Printed and Published for the KOYAL SOCIETY by 
HARRISON AND SONS, 44-47, ST. MARTIN’S LANE, LONDON, W.C. 2, 
Prtnter;S tn Ortrinarg to ^ajcstg. 
1920. 
Price Sixpence. 
A 681. 
8.6.20 
