I30 Mr. H. H. Howorth <?;2 



that during nearly the whole summer, while surrounded by 

 air above 32°, and itself at that temperature, it has acquired 

 a still greater degree of plasticity, due to the latent heat 

 which it has then absorbed (Forbes " Sixteenth Letter on 

 Glaciers," Ed. New Phil. Jour., Jan., 185 1). 



His opponents continued, however, to appeal to the 

 experience of hand specimens of ice, which are so brittle, 

 and whose behaviour seems so remote from that of plastic 

 bodies. In answer to them he writes : 



" I certainly never expected, when promulgating the 

 viscous theory, that it would have met with so much opposi- 

 tion on the ground that the more familiar properties of ice 

 are opposed to the admission of its plasticity : and that the 

 fragility of hand specimens should be considered as con- 

 clusive against the plastic effect of most intense forces 

 acting on the most stupendous scale upon a body placed in 

 circumstances which subject it to ia trial, beneath which the 

 most massive constructions of the pyramid building ages 

 would sway, totter, and crumble. ... in these days 

 when the barriers of the categories are so completely beaten 

 down, I had not expected to meet with so determined an 

 opposition to the proposition that the stupendous aggrega- 

 tion of freezing water and thawing ice called a glacier, 

 subjected to the pressure of thousands of vertical feet of its 

 own substance might not under these circumstances possess 

 a degree of yielding, moulding, self-adapting power, 

 sufficient to admit of slight changes of figure in long periods 

 of time. Still less could I have anticipated that when the 

 plastic changes of form had been measured, and com- 

 pared and calculated and mapped, and confirmed by 

 independent observers, that we should still have had men 

 of science appealing to the fragility of an icicle as an 

 unanswerable argument. More philosophical, surely, was 

 the appeal of the Bishop of Annecy from what we already 

 know to what we may one day learn if willing to be taught. 



