332 



JAMES CLERK MAXWELL. 



[CHAP. xi. 



of the plane of polarised light by magnetism is coming out 

 in the Phil. Mag. I shall send you a copy. 



To THE SAME. 



8 Palace Gardens Terrace, 

 Kensington, London, W., 28th January 1862. 



Some time ago, when investigating Bernoulli's theory 

 of gases, I was surprised to find that the internal friction 

 of a gas (if it depends on the collision of particles) should 

 be independent of the density. 



Stokes has been examining Graham's experiments on 

 the rate of flow of gases through fine tubes, and he finds 

 that the friction, if independent of density, accounts for 

 Graham's results, but, if taken proportional to density, differs 

 from those results very much. This seems rather a curious 

 result, and an additional phenomenon, explained by the 

 " collision of particles " theory of gases. Still one 

 phenomenon goes against that theory the relation between 

 specific heat at constant pressure and at constant volume, 

 which is in air = 1'408, while it ought to be 1*333. 



My brother-in-law, who is still with us, is getting better, 

 and had his first walk on crutches to-day across the room. 



To C. J. MONRO, Esq. 



8 Palace Gardens Terrace, 

 London W., 18th February 1862. 



.. r (Seed. 3d March.) 



I got your letter in Scotland, whither we had gone 

 for the Christmas holidays. I have been brewing Platonic 

 suds, but failed, owing I suppose to a too low temperature. 

 I had not read Plateau's recipe then. Some of the 

 bubbles on the surface lasted a fortnight in the air, but 

 they were scummy and scaly and inelastic. I shall take 

 more care next time. Elliot of the Strand (30) is going to 

 produce colour-tops, with papers from De La Eue, and direc- 

 tions for use by me ; and so I shall be put in competition 

 with the brass Blondin and the Top on the top of the Top. 



