132 OLDHAM: THE ST1UCTIRE OF THE HIMALAYAS, ETC. 



accuracy but, allowing for all possible over-estimates, it cannot 

 be put lower than one-third, and is probably not much over one- 

 halt", of the original extent. It will be seen that the two estimates 

 overlap, so that it is just possible to account for the support of the 

 range, by compression limited to the area covered by the hills ; 

 on the other hand, if we take the highest estimate derived from 

 the hypothesis and the lowest possible from observation, the 

 downward prominence produced by compression would have to be 

 reinforced by an equal bulk of material, of similar density, to pro- 

 vide sufficient support for the visible range. These may be regarded 

 as the extreme limits, and the most natural conclusion is that, 

 although simple compression might account for the whole of the 

 support, or might be unable to account for more than one-half, the 

 conditions lie somewhere between these two limits, and probably 

 nearer to the first than the second, so that we mav take it that, 

 on the hypothesis which is being considered, the greater part of 

 the support of the range would be provided by the compression, 

 whicli it has certainly undergone, though a small portion mav be 

 attributable to the invasion of material from outside. 



The specific question which had been put, of how far the ele- 

 vation of the Himalayas is the direct result of the compression 

 which they have undergone, seems to have been answered. An 

 hypothesis has been found which is in accord with observation, 

 not only within the limits of the range itself, but in the regions 

 outside the range, where structures closely related to it in geograph- 

 ical extent and. presumably, in origin, are met with. But before 

 this hypothesis can be accepted as in any degree satisfactory, it 

 is necessary to examine the other explanations which have been 

 offered at various times, and it will be of interest to pursue the 

 hypothesis which has been discussed somewhat further, to see 

 whether a satisfactory explanation can be found of the compression 

 which it makes mainly responsible for the elevation of the Himalayas. 



To take this last question first, it must be confessed that 

 Mr. Fisher's investigation gives no conclusive answer. He rejected 

 the obvious suggestion that it was due to the contraction of the 

 earth by cooling; the cause may be a real one, it provides a force 

 very many times more than adequate to produce the effect required, 

 but the possible range of motion is almost equally in defect of that 

 necessary to account for the compression which has taken place. 



[ ^80 j 



