PHILOSOPHICAL TRANSACTIONS 
OF THE 
ROYAL SOCIETY OF LONDON. 
Series A, Vol. 221. TITLE, &c. 
TITLE, CONTENTS, INDEX, &c. 
A, VOL. 221. 
Printed and Published for the ROYAL SOCIETY by 
HARRISON AND SONS, Ltd., 44-47, ST. MARTIN’S LANE, LONDON, W.C. 2. 
Printer^ in ©rtrinsrg to HtS #Ujesftg. 
1921. 
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A 593. 
16.3.21 
