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University of California Publications. 



[Geology 



movements are slow and continuous, but the treatises and text- 

 books on geology are lacking in a discussion of the question. 



In his principles of geology Lyell argues in a general way 

 in favor of the slow movements of the land, but he is concerned 

 more particularly with opposing the catastrophic ideas that were 

 current at the time. He points out that past actions are prob- 

 ably the same as those going on at present, that the continued 

 growth of corals on coral islands indicates, according to the 

 ideas of Darwin and Dana, a gradual subsidence and that no 

 sudden depression amounting to as much as 100 feet could have 

 taken place without the destruction of the life of the coral- 

 building polyps. He also argues that after earthquakes along 

 the South American coast, the land was found to be raised a 

 few feet, and considers that the great elevation of the coast 

 shown by raised beaches, etc., is simply the sum of these small 

 movements. He adduces the creep as observed in coal mines and 

 points out that the plastic floors of some mines are gradually 

 squeezed up to fill the space between the pillars left to support 

 the roof, and that this movement in general is slow and continued. 



Great weight is put on the slow changes of level in the Scan- 

 dinavian peninsula, which were at that time much discussed, 

 the movements of the temple of Serapis at Possuoli, and other 

 slow changes of level. Since Lyell 's time, many other similar 

 movements have been discovered. It has also been pointed out 

 that mountain ranges have been raised across the courses of 

 certain rivers, but that the elevation has been so slow that the 

 rivers have been aide to cut down their beds as fast as the' 

 mountains rose, and have thus preserved their original courses. 

 The course of the Potomac River, for instance, has not been 

 changed by the elevation of the Appalachians. 



It is quite evident that these arguments do not distinguish 

 between continuous slow movements, and a succession of small 

 sudden displacements, and Lyell was rather concerned with com- 

 batting the older catastrophic theory and advancing the uni- 

 formitarian ideas of Hutton. But, nevertheless, the universal 

 acceptance of Hutton 's views, and the lack of evidence that the 

 undoubtedly slow changes of level were the result of many small 

 but sudden movements, has led to the general belief that the 



