Ch. VII.] 



OF PARALLEL MOUNTAIN-CHAINS 



123 



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falling in along determinate lines of fracture. During such 

 a crisis the rocks are subjected to great lateral pressure, the 

 unyielding ones are crushed, and the pliant strata bent, and 

 are forced to pack themselves more closely into a smaller 



e same room 

 same time, i 



out horizontally. At the 

 mass is squeezed upwards, because it is in the upward direc- 

 tion only that the excess in size of the envelope, as compared 

 to the contracted nucleus, can find relief. This excess pro- 



& -~ «M A * -« i "^ #t 



mor 



mountain 



moder 



such as 



the Alps, which were partly upheaved after the middle ter- 

 tiary period. The elevation of the Andes was much more 



recent, and was 



accom 



simultaneous outburst 



for the first time of 270 of the principal volcanos now 

 active.* The agitation of the waters of the ocean caused by 

 this convulsion probably occasioned that transient and general 

 deluge which is noticed in the traditions of so 



many 



t 

 Several of the topics enumerated in 



summary 



such as the cause of interruptions in the sedimentary series, 

 will be discussed in the 14th chapter, and I shall now confine 

 myself to what I conceive to be the insufficiency of the 

 proofs adduced in favour of the suddenness of the upthrow, 

 and the contemporaneousness of the origin of the parallel 

 chains referred to. At the same time I may remark, that 



M. de Beaumont 



m 



tending 

 mountain 



as they 



do to confirm the doctrine that different 



have been formed in succession, and, as 



Werner first pointed out, that there are certain determinate 



lines of direction or strike in the strata of various countries. 



The following may serve as an analysis of the evidence on 



which the theory above stated depends. < We observe, 5 says 



M 



examine 



mountain-chains, that the most recent rocks extend hori- 

 zontally up to the foot of such chains, as we should expect 



* Systemes de Montagnes, p. 762. 



f Ibid. pp. 761 and 773. 



