PROCEEDINGS 
OF THE 
ROYAL SOCIETY OF EDINBURGH. 
SESSION 1906-7. 
No. III.] VOL. XX VII. [Pp. 161-288. 
CONTENTS. 
PAGE 
XVII. The Composition of the Red Clay. By F. W. Clarke, 
D.Sc., LL.D , Chief Chemist, U.S. Geological Survey. 
( Communicated by Sir John Murray, K.C.B., FR.S., 
etc.), . . . . . . .167 
{Issued separately July 19, 1907.) 
XVIII. The Physical Properties of Mixed Solutions of Independ- 
ent Optically- Active Substances. By Clerk Ranken, 
B.Sc., Carnegie Research Scholar, and W. W. Taylor, 
M.A., D.Sc. ( Communicated by Professor Crum 
Brown, F.R.S.), . . . . . .172 
( Issued separately July 19, 1907.) 
XIX. On Vibrating Systems which are not subject to the 
Boltzmann-Max well Law. (Second Paper.) By Dr W. 
Peddie, ....... 181 
{Issued separately August 28, 1907.) 
XX. On the Partition of Heat Energy in the Molecules of 
Gases. By Dr Paul Ehrenfest. ( Communicated by 
Dr W. Peddie.), . . . . . .195 
{Issued separately August 28, 1907.) 
XXI. Preliminary Note on the Internal Structure of Sigillaria 
mamillaris, Brongniart, and Sigillaria scutellata, 
Brongniart. By R. Kidston, F.R.S. L. & E., F.G.S., 
Foreign Mem. Kaiserl. Mineral. Gesell. zu St Petersburg, 203 
{Issued separately August 28, 1907.) 
[ Continued. 1. on page iv of Cover. 
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