20 JAMES CLERK MAXWELL. [CHAP. I. 



" Mr. Clerk of Eldin was another friend with whom, in 

 the formation of his theory, Dr. Hutton maintained a con- 

 stant communication. Mr. Clerk, perhaps from the exten- 

 sive property which his family had in the coal-mines near 

 Edinburgh, was early interested in the pursuit of mineralogy. 

 His inquiries, however, were never confined to the objects 

 which mere situation might point out, and through his whole 

 life has been much more directed by the irresistible impulse 

 of genius, than by the action of external circumstances. 

 Though not bred to the sea, he is well known to have 

 studied the principles of naval war with unexampled success ; 

 and, though not exercising the profession of arms, he has 

 viewed every country through which he has passed with the 

 eye of a soldier as well as a geologist. The interest he took 

 in studying the surface no less than the interior of the earth ; 

 his extensive information in most branches of natural history ; 

 a mind of great resource and great readiness of invention ; 

 made him to Dr. Hutton an invaluable friend and coadjutor. 

 It cannot be doubted that, in many parts, the system of the 

 latter has had great obligations to the ingenuity of the 

 former, though the unreserved intercourse of friendship, and 

 the adjustments produced by mutual suggestion, might 

 render those parts undistinguishable, even by the authors 

 themselves. Mr. Clerk's pencil was ever at the command 

 of his friend, and has certainly rendered him most essential 



In another place the same writer says : 



" Some excellent drawings were made by Mr. Clerk, 

 whose pencil is not less valuable in the sciences than in the 

 arts." l 



John Clerk, Esq., of Eldin, fifth son of Sir John Clerk of 

 Penicuik, and brother of Sir George, the grandfather of John 

 Clerk Maxwell, was the author of certain suggestions on Naval 

 Tactics, which had the credit of contributing to the victory 



1 See the collection of his etchings printed for the Bannatyne 

 Club in 1855, with a striking portrait of him. 



