PROCEEDINGS 
So 
OF THE 
ROYAL SOCIETY OF EDINBURGH. 
SESSION 1920-21 
Part II] VOL. XLI. [PP- 97-275 
(Contains Title, Contents, and Index.) 
CONTENTS. 
NO. PAGE 
X. An Experimental Analysis of the Losses by Evaporation of 
Liquid Air contained in Vacuum Flasks. By Professor 
Henry Briggs, D.Sc., Ph.D., A.R.S.M., .... 97 
( Issued separately June 20, 1921.) 
XI. Note on a Continuant of Cayley’s of the Year 1874. By Sir 
Thomas Muir, F.R.S., .111 
(. Issued separately August 23, 1921.) 
XII. On the Old Red Sandstone Plants showing Structure, from the 
Rhynie Chert Bed, Aberdeenshire. Part IV. Restorations 
of the Vascular Cryptogams, and discussion of their bear- 
ing on the General Morphology of the Pteridophyta and 
the Origin of the Organisation of Land-Plants. Part V. 
The Thallophyta occurring in the Peat Bed ; the Succes- 
sion of the Plants throughout a Vertical Section of the 
Bed, and the Conditions of Accumulation and Preservation 
of the Deposit. By R. Kidston, LL.D., D.Sc., F.R.S., and 
Professor W. H. Lang, D.Sc., F.R.S. [Abstract], . . .117 
(. Issued separately August 23, 1921.) 
XIII. The Adsorption of Gas under Pressure. By Henry Briggs, 
D.Sc., Ph.D., A.R.S.M., and William Cooper, M.A., B.Sc., . 119 
(. Issued separately August 23, 1921.) 
XIV. Utilisation of Solid Caustic Soda in the Absorption of Carbon 
Dioxide. By Elizabeth Gilchrist, ALA., B.Sc., A.I.C. 
Communicated by Professor Henry Briggs, D.Sc , Ph.D., 
A.R.S.M., .......... 128 
( Issued separately September 5, 1921.) 
XV. On the Criterion for Stable Flow of a Fluid in a Uniform 
Channel. By H. Levy, M.A., D.Sc., Assistant-Professor of 
Mathematics, Imperial College of Science, South Ken- 
sington, .......... 136 
{Issued separately December 13, 1921.) 
XVI. Note on Conditions for Mirage on the Queensferry Road. 
By Alex. G. Ramage, 148 
{Issued separately December 13, 1921.) 
[Continued on 
EDINBURGH: 
Published by ROBERT GRANT & SON, 107 Princes 
WILLIAMS & NORGATE, 14 Henrietta Street, Covent Garden, 
Price Eight Shillings. 
