CHAP. XL] LETTERS FROM GLENLAIR. 343 



The Eoyal Society of Edinburgh used to be a very 

 sociable body, but it had several advantages. Most of the 

 fellows lived within a mile of the Society's rooms. They 

 did not need to disturb their dinner arrangements in order 

 to attend. 



Many of them were good speakers as well as sensible 

 men, whose mode of considering a subject was worth hearing, 

 even if not correct. 



The subjects were not limited to mathematics and physics, 

 but included geology, physiology, and occasionally antiquities 

 and even literary subjects. Biography of deceased fellows 

 is still a subject of papers. Now those who cultivate the 

 mathematical and physical sciences are sometimes unable to 

 discuss a paper, because they would require to keep it some 

 days by them to form an opinion on it, and physical men 

 can get up a much better discussion about armour plates or 

 the theory of glaciers than about the conduction of heat or 

 capillary attraction. 



The only man I know who can make everything the 

 subject of discussion is Dr. Tyndall. Secure his attendance 

 and that of somebody to differ from him, and you are all 

 right for a meeting. 



If we can take the field with a plan in our head, I dare 

 say we could find a good many men who would co-operate. 



We ride every day, sometimes both morning and evening, 

 and so we consume the roads. I have made 68 problems, 

 all stiff ones, not counting riders. 



I am now getting the general equations for the motion 

 of a gas considered as an assemblage of molecules flying 

 about with great velocity. I find they must repel as inverse 

 fifth power of distance. 



To C. H. CAY, Esq. 



Gknlair, 14th October 1865. 



... I hope you keep your conscience in good order, and 

 do not bestow more labour on erroneous papers than is useful 

 to the youth who wrote it. Always set him to look for the 

 mistake, if he prefers that to starting fresh, for to find your 



