453 THE LIFE OF JAMES D. FORBES. [CHAP. 



execution a calm, clear, and perfectly unbiassed judgment. 

 In this respect, no man could have been found more 

 excellently qualified than Forbes. No man was ever 

 more strictly conscientious, or more thoroughly dis- 

 passionate ; as is amply proved by the Dissertation 

 itself, in which he had to deal with several very delicate 

 matters such as, for instance, the discovery of Neptune. 

 In this work the author himself is one of the few to 

 whose claims substantial justice has not been done. He 

 detested controversy and, though (as is usually the case 

 with peaceful men) often forced to take part in it, did so 

 solely for truth's sake, never for the exaltation of himself 

 or for the humiliation of his adversary. 



Perhaps the most prominent of Forbes' investigations 

 is that long series devoted to the nature and motion of 

 Glaciers, which he pursued with intense application, and 

 to the serious, possibly the lasting, injury of his health. 

 The result was an account, of the structure and nature 

 of the motion of these marvellous ice-masses, so full 

 and luminous that very little indeed has since been 

 added to it. While preserving what was true in the mass 

 of statements made by his predecessors, he replaced an 

 immense amount of nonsense by many new facts of the 

 very highest order of importance. Critics have attempted 

 to show that he had been anticipated in some of these ; 

 but they have produced only vague statements, probably 

 meant in a totally different sense. Considerable con- 

 fusion seems still to obscure the common apprehension of 

 what Forbes really did. His careful observations led him 

 to the general proof that a glacier moves like a viscous 

 or plastic mass, though ice is usually regarded as a very 

 brittle solid. Here no physical explanation is involved. 

 In virtue of what property the ice behaves in this way 

 is quite another question, and one the answer to which 

 is even yet in some parts obscure, though there can be 

 no doubt that a very important contribution, at least, is 

 furnished by the beautiful discovery of James Thomson 

 regarding the lowering of the freezing-point by pressure. 

 It is not very easy to discover which theory appeared 



