250 JAMES CLERK MAXWELL. [CHAP. IX. 



I told Willie (Cay) how I had hung up a bullet by a 

 combination of threads. 



I have drawn from theory the curves which it ought to 

 describe, and when I set the bullet a-going over the proper 

 curve, it traces it out over and over again as if it were doing 

 a pre-ordained dance, and kept a steady eye on the line on 

 the paper. I have enlarged my stock of models for solid 

 geometry, made of coloured thread, stretched between two 

 pasteboard ends. 



FROM PROFESSOR J. D. FORBES. 



Edinburgh, 13th Feb. 1856. 



You may not perhaps have heard that Mr. Gray, Pro- 

 fessor of Natural Philosophy, Marischal College, Aberdeen, is 

 dead. He was a pleasing and energetic person, in the prime 

 of life and health, a few months ago, when I saw him last. 



I have no idea whether the situation would be any 

 object to you ; but I thought I would mention it, as I think 

 it would be a pity were it not filled by a Scotchman, and 

 you are the person who occurs to me as best fitted for it. 



Do not imagine from my writing that I have the 

 smallest influence in the matter, or interest in it beyond the 

 welfare of the Scottish Universities. 



It is in the gift of the Crown. The Lord Advocate and 

 Home Secretary are the parties to apply to. I am not 

 acquainted with either. 



In the Commissioners' Eeport of 1830 the emoluments 

 are stated at about 350. But they are not always to be 

 depended upon. 



Another point. I think you ought certainly to be a 

 Fellow of the Eoyal Society of Edinburgh. I shall be glad 

 to propose you if you wish it. 



To HIS FATHER. 



Trin. Coll, 15th Feb. 1856. 



Professor Forbes has written to me to say that the 

 Professorship of Nat. Phil, at Marischal College, Aberdeen, 

 is vacant by the death of Mr. Gray, and he inquires if I 



