[ 
431 
] 
INDEX 
TO THE 
PHILOSOPHICAL TRANSACTIONS. 
Series A, Vol. 221. 
A. . 
Aberration, theory of second order longitudinal spherical (Bakbb and 29. 
Aerodynamics of spinning shell (Fowleb and others), 295. 
Atmospheric turbulence, measurements of (Richaedson), 1. 
B. 
Bakek (T. T.) and Filoh (L. IN'. G.). On a Theory of the Second Order Longitudinal Spherical Aberration for a 
Symmetrical Optical System, 29. 
C. 
CflAKE'o (E. C.). See Cokeb and Chakko. 
Cokeb (E. G.) and Chakko (K. C.). The Stress-strain Properties of Nitro-cellulose and the Law of its Optical Behaviour, 
139. 
D. 
Dalby (V. E.). Researches on the Elastic Properties and the Plastic Extension of Metals, 117. 
E. 
Error, reduction by linear compounding (Sueppabd), 199. 
F. 
Filon (L. X. G.). See Bakeb and Filon. 
Fowleb (R. H.) (and others). The Aerodynamics of a Spinning Shell, 295. 
G. 
Gallop (E. G.). See Fowleb and others. 
Gbipfith (A. A.). The Phenomena of Rupture and Flow in Solids, 163. 
J. 
Jeffeby (G. B.). Plane Stress and Plane Strain in Bipolar Co-ordinates, 265. 
Jeffeeys (H.). Tidal Friction in Shallow Seas, 239. 
3 o 
VOL. COXXI.-A. 
[Published March 16, 1921. 
