130 



THEORY OF SUDDEN ELSE OF 



[Ch. VII, 





Cfl 



Hopkins admits that the exterior of the planet, though solid 

 as a whole, may contain within it vast lakes or seas of lava. 

 If so the gradual fusion of rocks, and the expansive power of 

 heat exerted for ages, as well as the subsequent contraction 



mountain 



»n, may perhaps account 

 for these, as Dolomieu 



has remarked, are ' far less important, proportionally speak- 

 ing, than the inequalities on the surface of an egg-shell, 

 which to the eye appears smooth.' A ' centripetal force ' 



affectino- the whole planet as it cools, seems a mignuer cause 

 than is required to produce wrinkles of such insignificant 



size. 



In pursuing his investigations, M. E. de Beaumont has of 

 late greatly multiplied the number of successive periods of 

 instantaneous upheaval, admitting at the same time that 

 occasionally new lines of upthrow have taken the direction of 

 older ones * These admissions render his views much more 

 in harmony with the principles advocated in this work, but 

 they impair the practical utility of parallelism considered as 

 a chronological test ; for no rule is laid down for limiting 

 the interval, whether in time or space, which may separate 

 two parallel lines of upheaval of different dates.f 



Among the various propositions above laid down (p. 122), 

 it will be seen that the sudden rise of the Andes is spoken 

 of as a modern event, but Mr. Darwin has broi 

 ample data in proof of the local persistency of volcanic action 

 throughout a long succession of geological periods, begin- 

 ning with times antecedent to the deposition of the oolitic 

 and cretaceous formations of Chili, and continuing to the 

 historical epoch. It appears that some of the parallel ridges 

 which compose the Cordilleras, instead of being contem- 

 poraneous, were successively and slowly upheaved at wide y 

 different epochs. The whole range, after twice subsiding 



* Art. Systemes de Montagnes, p. intersect each other at certain angles, so 



775. as to produce a regular geometric ^ 



f M. E. de Beaumont in his later rangement, which he calls ' a P enta 2 ^ 



enquiries (Comptes rendus, Sept, 1850, network.' This theory has *** n iJ. 



and Systemes de Montnmies) has come discussed and controverted by Mr V 



to the conclusion, that the principal kins, in his Anniversary auu * 



mountain ranges, if prolonged, would President of the Geol. Soc, -t e 









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