PHILOSOPHICAL 
TRANSACTIONS 
OF THE 
ROYAL SOCIETY OF LONDON. 
Series A. 
CONTAINING PAPEES OF A MATHEMATICAL OK PHYSICAL CHARACTEE. 
VOL. 219. 
Printed and Published for the ROYAL SOCIETY by 
HARRISON AND SONS, 44-47, ST. MARTIN’S LANE, LONDON, W.C. 2, 
printers in #rbinarg to ^is P^ajtstg. 
July, 1919. 
