AKD MODEfcN PHYSICS. 49 



planet exterior to Uranus." Professor Challia, Dr. 

 Parkinson, and Sir William Thomson, the examiners, 

 had selected as the subject for the prize to be awarded 

 in 1857 the "Motions of Saturn's Rings." For this 

 Maxwell had decided to compete, and his letters at 

 the end of 1857 tell of the progress of the task. 

 Tims, writing* to Lewis Campbell from Glenlair on 

 August 28th, he says : 



" I have been battering away at Saturn, returning to the 

 charge every now and then. I have effected several breaches 

 in the solid ring, and now I am splash into the fluid one, amid 

 a clash of symbols truly astounding. When I reappear it will 

 be in the dusky ring, which is something like the state of the 

 air supposing the siege of Sebastopol conducted from a forest 

 of guns 100 mile* one way, and 30,000 miles the other, and the 

 shot never to srop, but go spinning away round a circle, radius 

 170,000 miles." 



And again t to Miss Cay on the 28th of November: 



" I have been pretty steady at work since I came. The 

 class is small and not bright, but I am going to give them 

 plenty to do from the first, and I find it a good plan. I have 

 a large attendance of my old pupils, who go on with the higher 

 subjects. This is not part of the College course, so they come 

 merely from choice, and I have begun with the least amusing 

 part of what I intend to give them. Many had been reading 

 in summer, for they did very good papers for me on the old 

 Bubjects at the beginning of the month. Most of my spare 

 time 1 have been doing Saturn's rings, which is getting on 

 now, but lately I have had a great many long letters to write 

 some to Glenlair, some to private friends, and some all about 

 science. ... I have had letters from Thomson and Challis 

 about Saturn from Hayward, of Durham University, about 



" Life of J. C. Maxwell," p. 278. 

 t Life of J. C. Maxwell," p. 292. 



