134 OLDHAM: THE STRUCTURE OF THE HIMALAYAS, ETC. 



Face of the Earth, has attained a certain vogue, and a con- 

 siderable amount of influence on geological thought and specu- 

 lation. This explanation is based on the hypothesis of an originally 

 highly heated solid globe gradually cooling by radiation from the 

 surface, and the effects of surface deformation are attributed to the 

 compression, to which the outer layers of the earth would be 

 subjected, by the gradual contraction of such a globe. In ex- 

 plaining the actual forms, assumed by the surface, great stress is 

 laid on the supposed directions from which pressure was applied, 

 and to which movement took place. In the case of the Hima- 

 layas it is specially argued x that the form of the range, and of the 

 associated ranges on the eastern and western frontiers of India, 

 can only be explained if pressure was applied from outside towards 

 the steady mass of the Peninsula, and is inconsistent with the 

 supposition that the pressure and movement came from the south. 

 On this view of the case the peninsular area naturally became a 

 foreland, and the Gangetic trough a foredeep ; but the whole of the 

 reasoning, on which the conclusion is based, is permeated by two 

 mechanical fallacies. 



The first is the possibility of a one-sided application of pressure ; 

 but pressure can only exist if there is some resistance, and the 

 resistance necessarily gives rise to an equal and opposite pressure. 

 If these opposing pressures exceed the resistance of the material, 

 compression, and consequent movement, will take place, but the 

 direction and form, which this yielding will assume, is dependent 

 solely on the nature of the resistances, and the amount of move- 

 ment needful to relieve the pressure. The other fallacy is the 

 possibility of absolute movement, and this will be most easily 

 explained by reference to a diagram ; in fig. 11 let A B be two 



•0 



<*3 



Fig. 11. 



points near the outer limit of the. Himalayas, C a point welj away 

 to the northwards and D one well away to the southwards, and 



1 Das Antlitz der Eric, III (2), p. 707. English translation IV, p. 614. 



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