1844.] ICE MAY BE RENT AND REUNITED. 53 



applied on a great scale to bodies, are the best and only con- 

 clusive proofs of their real constitution, and worth all molecular 

 theories and minute experiments put together. 



If a body be really of a pasty consistence, ductile and plas- 

 tic like lava or tar, such transpositions taking place in the 

 interior of the mass are effected without any injury to the tex- 

 ture or continuity of the substance. With a degree less of 

 plasticity, a violent separation of the parts may take place, but 

 they will, by juxtaposition, soon reunite and take a new set. 

 With a degree more of rigidity, there must be a permanent 

 'bruising and rending of the parts, in order that a semirigid 

 body may assimilate in all its movements to a fluid. It must, 

 therefore, be considered as entirely confirmatory and explanatory 

 of the preceding statements of the seeming plasticity of a body 

 so fragile in its elements as pure ice, that the ice of glaciers is 

 found rent in many parts by the forces tending to dislocation, 

 and that, besides, it contains within itself a testimony to the 

 internal partial movements by which its total motion is effected, 

 in the veined structure already alluded to, occasioned by the 

 varying velocity of the adjacent icy strips A. a a a", B b b' l>", 

 etc. This structure is not exactly parallel to the direction of 

 motion of the ice, for reasons which I have elsewhere stated, 

 but which need not now be adverted to. My present object is 

 to shew, that the rigidity of ice, as a physical fact, cannot con- 

 tradict the mathematical evidence of the manner in which 

 glaciers do move, and that the seeming contradiction is recon- 

 ciled by showing, that the ice bears permanent traces of the 

 violent strain to which it is subjected, and of the actual bruising 

 and disseverment of its parts, producing a phenomenon otherwise 

 impossible to be explained. 



I believe that it is during the progress of the glacier thus 

 subjected to a new and peculiar set of forces depending upon 

 gravity, and which remodel its internal constitution, by sub- 

 stituting hard blue ice, in the form of veins, for its previous 

 snowy texture, that the horizontal stratification observed in the 

 higher part of the glacier or nM, is gradually obliterated. 



