* 



°05 



CHAPTEE XIV. 



UNIFORMITY IN THE SEEIES OF PAST CHANGES IN THE 



ANIMATE AND INANIMATE WORLD. 



SUPPOSED ALTERNATE PERIODS OF REPOSE AND DISORDER— OBSERVED FACTS 

 IN WHICH THIS DOCTRINE HAS ORIGINATED — THESE MAY BE EXPLAINED BY 

 SUPPOSING A UNIFORM AND UNINTERRUPTED SERIES OF CHANGES — THREE- 

 FOLD CONSIDERATION OF THIS SUBJECT ; FIRST, IN REFERENCE TO THE 

 LAWS WHICH GOVERN THE FORMATION OF FOSSILIFEROUS STRATA, AND THE 

 SHIFTING OF THE AREAS OF SEDIMENTARY DEPOSITION ; SECONDLY, IN RE- 

 FERENCE TO THE LIVING CREATION, EXTINCTION OF SPECIES, AND ORIGIN OF 

 NEW ANIMALS AND PLANTS ; THIRDLY, IN REFERENCE TO THE CHANGES 

 PRODUCED IN THE EARTH'S CRUST BY THE CONTINUANCE OF SUBTERRANEAN 

 MOVEMENTS IN CERTAIN AREAS, AND THEIR TRANSFERENCE AFTER LONG 

 PERIODS TO NEW AREAS — ON THE COMBINED INFLUENCE OF ALL THESE 

 MODES AND CAUSES OF CHANGE IN PRODUCING BREAKS AND CHASMS IN THE 



CHAIN OF RECORDS CONCLUDING REMARKS ON THE IDENTITY OF THE 



ANCIENT AND PRESENT SYSTEM OF TERRESTRIAL CHANGES. 



Origin of the doctrine of alternate periods of repose and 

 disorder. — It has been truly observed, that when we arrange 

 the fossiliferous formations in chronological order, they con- 

 stitute a broken and defective series of monuments : we pass 

 without any intermediate gradations from systems of strata 



which are horizontal to other systems which are highly inclined, 



from rocks of peculiar mineral composition to others which 

 have a character wholly distinct, — from one assemblage of 

 organic remains to another, in which frequently nearly all the 

 species, and a large part of the genera, are different. These 

 violations of continuity are so common, as to constitute, 

 even in districts of considerable area, the rule rather than the 



exception, and they have been considered by many geologists 



as conclusive in favour of sudden revolutions in the inanimate 

 and animate world. We have already seen that according 

 to the speculations of some writers, there have been in the 

 past history of the planet alternate periods of tranquillity and 



VOL. I. 



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