" BRUISING AND RE-ATTACHMENT." Xvii 



in 1857 : If it shall be further found that I argued from nature's 

 own experiment on the modelling of ice on the great scale in the 

 irregular cavities of a mountain valley, to the same purpose as 

 Dr. Tyndall does from his beautiful laboratory experiment, 

 whence he retraces the steps of the process to apply it to the 

 actual glacier, and that there is no reason for accepting the ex- 

 periment in the laboratory as more certain or more conclusive 

 than the observation in the mountain valley, but that each obser- 

 vation confirms and illustrates the other : Should all this be 

 admitted on due examination, I shall, I trust, still be held to 

 have laid just and solid foundations for a Plastic or Viscous 

 Theory of Glaciers, without the desire or pretension to have 

 credit for exhausting the subject in such a manner tl&t future 

 discoveries in physics can throw no more light upon it. . I 

 utterly disclaim so unworthy a pretension, and I appeal to every 

 passage of my writings in which I have referred to the more 

 obscure questions of physics and mechanics, as bearing on the 

 Glacial Theory, in corroboration of this statement. 



I am aware that when the Theory of Glaciers was again 

 in 1857 brought under discussion in the way I have already 

 mentioned, it was not easy for those who desired to know what 

 could be said for the Plastic Theory to obtain an exact acquaint- 

 ance with all that had been urged in its favour, or with the 

 modifications, if any, of the author's original views derived from 

 farther experience or consideration. Some might hold that the 

 " Travels in the Alps," as published in 1843, contained the 



work : The body of the glacier itself . . . yields, owing to its slightly ductile 

 nature, in the direction of least resistance, retaining its continuity, or recovering it 

 by re-attachment after its parts have suffered a bruise, according to the violence of 

 the action to which it has been exposed," p. 166. " In this condition [on the ' very 

 border of thawing'] molecular attachment amongst the granules must be com- 

 paratively easy, and the opacity disappears in proportion as optical contact is 

 attained," p. 201. "Multitudinous incipient fissures occasioned by the intense 

 strain are reunited by the simple effects of time and cohesion." Hid. 



