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Most of the other objections to the hypothesis of isostasy are well 

 formulated and some of them appear unsurmountable. 



In conclusion the author says: "The considerations presented in 

 the foregoing paper indicate that, while the greater inequalities of the 

 earth's surface, such as the continental arches and the oceanic depres- 

 sions, may exist by reason of isostasy, the mass of available evidence is 

 opposed to the view that denudation and sedimentation are able to 

 produce movements in the earth's crust, as direct consequences of the 

 weight of the material shifted. Not only do such superficial processes 

 seem inadequate to initiate deep-seated crustal movements, but, as far 

 as we can see, the movements, even when initiated through other 

 causes, are as indifferent to such processes as is a slumbering volcano 

 to the changes wrought by human tillage upon its flanks." 



Mr. Reade's most recent references to the hypothesis of isostasy 

 are contained in the presidential address to the Liverpool Geological 

 Society in which he describes briefly the geology of the British Isles in 

 relation to mountain building. The allusions to isostasy are inci- 

 dental rather than specific and the conclusions to be deduced are 

 against the theory. In this connection he gives a summary of his 

 latest opinions regarding the cause of orogenic movements and ascribes 

 them entirely to changes of temperature, producing expansion and 

 contraction, and not to the shrinkage of the nucleus of the earth, the 

 closing in of the non-shrinking crust upon it and the consequent fold- 

 ing by tangential pressure. In concluding he says: that "Neither 

 does the principle of isostasy so insisted upon by American geologists 

 explain the compression, folding and building up of great masses of 

 sediment into mountain ranges. On the principle of isostasy, it must 

 be obvious to anyone possessing even a rudimentary acquaintance 

 with mechanics that the sinking of the bed of the seas on which great 

 deposits are accumulating, and to some extent a rise of surrounding 

 land, may be explained, but not the lateral compression and elevation 

 of the sediments themselves into mountain ranges." 



Mr. Gilbert's notes are of great interest at this time. They are 

 based upon a series of trans-continental gravity determinations made 

 by Mr. G. R. Putnam, and are appended to the latter's article. As 

 generally understood isostasy is intended to cover those oscillations 

 which are the direct result of local or provincial loading and unloading. 

 This appears to be the specific limitation placed upon the hypothesis 

 by Messrs. Button and McGee. Mr. Gilbert, however, uses the term 



