Geology 



them, in most of which deluges, conflagrations, and 

 earthquakes figured largely. 



As opposed to this older catastrophic school, the 

 modern geologist believes that most, if not all, of the 

 great physical features have been formed slowly by 

 forces acting quietly, for the most part, through long 

 ages of time. 



It was about the middle of the eighteenth century 

 that James Hutton of Edinburgh, who had given much 

 time and energy to the study of the Earth's history, 

 enunciated what is since known as the doctrine of 

 uniformity. His doctrine was simply that the rocks had 

 been produced by agencies still at work, and that the 

 speed at which these agencies acted had not appreciably 

 changed throughout geological time ; that the valleys 

 of the past were carved out by the streams just as the 

 streams of to-day are deepening their courses, and that 

 the seas of past periods received the detritus of the land 

 to build up the rocks of the present continents, just as our 

 oceans are elaborating the materials of lands still to come. 



In the early part of the nineteenth century William 

 Smith, a civil engineer, discovered a fact and enunciated 

 a principle which has done more to further geological 

 science than anything which had been previously added 

 to our knowledge. 



We have already seen that certain aquatic animals 

 contribute largely to the formation of rock materials, 

 and it frequently happens that the whole animal, or 

 some recognizable part of it, is preserved in the mass, 

 thus forming a record of the past inhabitants of the 

 globe. These remains of plants and animals, often con- 

 verted into substances quite other than those of the 



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