287 



paired before the ensuing spring, I there observed, *' The main cause 

 of the restoration of the surface is the diminished fluidity of the 

 glacier in cold weather, which retards (as we know) the motion of all 

 its parts, but especially of those parts which move most rapidly in 

 summer. The disproportion of velocity throughout the length and 

 breadth of the glacier is therefore less, the ice more pressed together, 

 and less drawn asunder ; the crevasses are consolidated, while the 

 increased friction and viscosity causes the whole to swell, and espe- 

 cially the inferior parts, which are the most wasted." — (See also 

 Seventh Letter on Glaciers ^ p. 435 of Appendix to the same 

 work.) 



The following Gentleman was elected an Ordinary Fel- 

 low : — 



Dr Stevenson Macadam. 



Monday t l^th February 1855. 



JAMES TOD, Esq., in the Chair. 



The following Communications were read : — 



1. On the Mechanical Action of Heat : — Supplement to the 

 first Six Sections, and Section Seventh. By W. J. Mac- 

 queen Rankine, Esq., C.E., E.R.SS. Lond. and Edinb. 



This paper is written in continuation of a series of papers, of which 

 six sections have already been published in the Transactions of the 

 Royal Society of Edinburgh. 



It commences with some articles supplementary to the first six 

 sections, and intended to apply to the theoretical principles contained 

 in them to the extensive and precise experimental data which have 

 been obtained in the course of the last two years. 



Article 65 relates to the Absolute Thermometric Scale and to 

 Thermodynamic Functions. The Absolute Thermometric Scale is 

 a scale, the temperatures on which, according to one definition, are 

 proportional to the actual quantity of energy possessed by any given 

 substance in the form of heat, divided by the real specific heat of the 



