202 Proceedings of the Boyal Society of Edinburgh. 



tbe barometer and the thermometer. This change was brought 

 about by the advent of two storms:, which came from southern lati- 

 tudes, and one or pei-haps both of which had, on the morning of the 

 27th, begun to affect the upper regions of the atmosphere, and load 

 them with warm vapour. 



2. Memorandum on the Intensity of Reflected Light and 

 Heat. By Professor Forbes. 



April 1. — Dr Hope, Vice-President, in the Chair. The fol- 

 lowing communications were read : — 



1. On the Theory of the Motion of Waves. By Professor 



Kelland. 



2. On a New Method of shewing the Unequal Expansion of 



Crystals. By Professor Forbes. 



April 15. — Lord Greenock in the Chair. The following 

 communications were read : — 



1. Notice respecting the relative Voltaic agency of Circuits of 



Copper and Zinc, and Zinc and Iron. By Martyn Ro- 

 berts, Esq. Communicated by the Secretary. 



2. Investigation of analogous properties of Co-ordinates of 

 Elliptic and Hyperbolic Sectors. By W. Wallace, 

 LL.D., Emeritus Professor of Mathematics, University 

 of Edinburgh. 



3 On the Newer Tertiary or Pliocene Deposites of Scotland. 

 By James Smith, Esq. of Jordanhill. 



I;. On certain circumstances affecting the Colour of Blood 

 during Coagulation. By Dr P. K. Newbigging. Com- 

 municated by Professor Forbes. 



The author described in this paper certain anomalous appearances 

 presented by venous b^ood when left in contact with coloured porce- 

 lain. When blood drawn from a vein is either allowed to coagu- 

 late in a porcelain cup, or after coagulation is left in it for some hours, 

 the dark purple tint characteristic of venous blood is found to be 

 altered to the bright arterial hue, wherever it was in contact with 

 any elevated device of the green colour, which is communicated by 

 means of protoxide of chrome. In one instance the same effect was 



