REPORT OF MEETINGS FOR 1902 233 



depression into which the materials worn off the upland areas 

 sooner or later find their way, and thus give rise to newer 

 sets of strata. 



Reasoning back from effects to causes, we may assert with 

 confidence that where we meet with highly convoluted rocks 

 like those, for example, which are so magnificently displayed 

 on the Berwickshire coast between St. Abbs and the Siccar 

 Point, those convolutions bear witness to the former existence 

 of great terrestrial thrusts which were exerted in directions 

 perpendicular to the axes of the folds ; they tell of enormous 

 upheavals over that spot — for no such crumpling is possible 

 except under the pressure of a stupendous pile of overlying 

 strata ; lastly, as these hatter are wanting, their absence 

 points to waste and destruction on a most extensive scale. 

 At what rate that waste may have gone on it is not easy 

 to say. Dr doll and others have collected evidence to show 

 that at the present day the rate, taking the world all over, 

 may be set at an average of about one foot in six thousand 

 years. Doubtless the rate would be much higher than that 

 in upland tracts, and one might, in allowing for that possibility, 

 set the rate at half that, so as to keep well within the mark. 



Now the next step in the argument, admitting that the 

 foregoing reasoning is sound, is to determine at what period 

 the waste in question took place. This is easily settled, because 

 the volcanic and associated rocks which form the Cheviots 

 and the Pentland Hills lie quite undisturbed across the ends 

 of the highly convoluted Silurian and older strata. The 

 crumpling of the rocks, the formation of the continental 

 masses, and the subsequent waste of the land so formed 

 must, therefore, have all taken place in the interval between 

 the close of the highest (or Lanarkian Rocks) and the 

 commencement of the conditions to which the succeeding strata 

 are due. There is no escaping this conclusion. Moreover, it 

 can be shown that the waste which ended in the interval of 

 time between the close of the Silurian Period and the 

 commencement of the next, which we will call the Devonian 

 Period, was of sufficient length to permit of the removal of 

 a vast thickness of the rocks older than the Silurians (the 

 Ordovician and older rocks) as well. The evidence upon that 

 point also does not admit of a doubt. 



