PKOCEEDINGS 



OF THE 



CAMBEIDGE PHILOSOPHICAL 

 SOCIETY 



VOLUME XX 



26 January 1920—16 May 1921 



CAMBRIDGE 



AT THE UNIVERSITY PRESS 



and sold by 



deighton, bell & co., ltd. and bowes & bowes, cambeidge 



cambridge university press 

 c. f. clay, manager, fetter lane, london, e.c. 4 



1921 



