232 REPORT OF MEETINGS FOR 1902 



This little experiment seems almost too trivial a matter to 

 make more than the very briefest reference to. Yet the same 

 principle which has regulated both the outward form of the 

 pile, and the shape assumed by its component straps, has 

 been in action again and again at many periods of the Earth's 

 history in giving rise to both the convolutions of strata 

 and the concurrent upheaval of great mountain masses. For 

 the straps substitute piles of rock ; for the compressing force 

 exerted by the hands think of the powerful forces that give 

 rise to the upheaval of continents and the correlative depression 

 of the floor beneath the oceans ; for the few minutes that 

 the experiment has taken to perform substitute in the mind 

 many millions of years ; for the tiny folds of the leathern 

 straps conceive of great convolutions affecting large areas of 

 country ; and for the vertical displacement of the pile of 

 straps undergoing compression substitute great upland areas, 

 hundreds of square miles in extent. There is one point, 

 however, where the parallel does not hold good. In nature, 

 as the upward fold progresses and the central area is more 

 and more raised, atmospheric forces, rain, rivers, and glaciers, 

 split up and waste the newly elevated rocks at a rate 

 proportionate to the degree of elevation ; so that it often 

 happens that the upheaving force and the rate of waste of 

 the newly-elevated laud so nearly balance each other that 

 the compressing force does not always result in much, or at 

 all, increasing the elevation. If the experiment with the straps 

 be repeated with this idea in mind, it will be noticed that the 

 crumpling of the inner parts of the lower straps is more 

 marked than it is in the case of the outer. This is another 

 way of stating the fact that the core of a region undergoing 

 upheaval will show much more intense crumpling than the 

 parts which are the earlier to reach the surface. As the 

 waste over the axis of upheaval proceeds, strata of an 

 increasingly crumpled and disturbed nature tend more and 

 more to the surface. 



The crumpling force, therefore, accomplishes three results. 

 It folds the strata, it causes inequalities of level at the surface, 

 and it places rocks over the zones of uprise under the most 

 favourable conditions for rapid waste by subaerial agencies, 

 and over the zones of downfolding it forms areas of 



