218 Proceedings of the Royal Society of Edinburgh. [Sess. 
The Makdougall-Brisbane Prize for the period 1918-1920 is awarded to Professor J. H. 
Maclagan Wedderbukn of Princeton University for the many valuable memoirs which he has 
published in our Transactions and Proceedings and elsewhere. One of these memoirs falls within 
the period of award of the prize — “On the Equations of Motion of a Single Particle.” Among 
the other memoirs may be mentioned — 
Isoclinal Lines of a Differential Equation of the 1st Order. Proc.R.S.E., vol. xxiv, p. 400, 
1903. 
General Scalar Functions of a Vector. Proc.R.S.E vol. xxiv, p. 409, 1903. 
Applications of Quaternions in the Theory of Differential Equations. Trans.R.S.E. , vol. 
xl, p. 709, 1903. 
And a number of important papers on Hypercomplex Numbers published in the Transactions of the 
American Mathematical Society. 
By request of the Council, Mr 0. T. R. Wilson, M.A., B.Sc., F.R.S. , gave an address on 
“ Some Recent Work on Lightning and Thunderstorms.” 
The following Communications were submitted : — 
1. The Adsorption of Gas under Pressure. By Professor Henry Briggs, D.Sc., and Wm. 
Cooper, M.A., B.Sc. Proc., vol. xli, pp. 119-127. 
2. The Utilisation of Solid Caustic Soda in the Absorption of Carbon Dioxide. By Miss 
Elizabeth Gilchrist, M.A., B.Sc, Communicated by Professor Henry Briggs, D.Sc. Proc., 
vol. xli, pp. 128-135. 
3. On the Development of the Feathers of the Duck during the Incubation Period. By Miss 
Augusta Lamont, B.Sc. Communicated by Professor J. Cossar Ewart, F.R.S. 
4. Note on Conditions for Mirage. By Alex. G. Ramage. Proc., vol. xli, pp. 148-149. 
