212 GLIMPSES OF NATURE. 



cost of labour in the lasting nature of the edifice 

 have raised. The rock in the quarry, you observe, 

 does not exist in one great mass. 



On the contrary, you see therein the same appear- 

 ance which has often met your eye as you have dashed 

 through many a railway cutting at breakneck speed. 

 It lies in " strata," as the geologist terms them long 

 and fairly regular bands of rock, varying in thickness 

 or depth. This disposition of the rock of the quarry 

 in layers, or strata, is in itself an important matter in 

 so far as the history of the rocks is concerned. For 

 this layered arrangement indicates first of all that the 

 rocks were formed in water and by the agency of water. 

 Let us see whether we may be able to glance back- 

 wards in the past with any hope of arriving at a clear 

 conclusion about the forces and conditions which were 

 responsible for the making of this huge mass of build- 

 ing stone, which man has found so useful for the 

 purposes of his life. 



How we gain a knowledge of the past of our globe 

 often forms a matter puzzling enough to the uninitiated 

 mind. Events in the history of our world such as 

 the making of the coal, the formation of chalk, the 

 growth of the old red sandstone, or the becoming of 

 the Silurian rocks occurring ages and ages before the 

 advent of man, are described by geologists with an 

 accuracy which almost bespeaks the eye of the observer. 

 We can tell to-day much of the history of the changes 

 which have occurred in land and sea, in Europe and 

 elsewhere, with a near approach to certainty ; and all 

 this " prophesying after the event," as it seems, is 

 wonderful enough to cause us to ask how geology 

 acquires its knowledge about the world the history 

 of the quarry included 



