

117 



■■. 



I 



* 





V | 





CHAPTER VII. 



Ul 



ON THE SUPPOSED FORMER INTENSITY OP THE IGNEOUS 



FORCES. 







~ 





die 



• 







T ■ 



* 



it -. 







- 



VOLCANIC ACTION AT SUCCESSIVE GEOLOGICAL PERIODS PLUTONIC ROCKS OF 



DIFFERENT AGES — GRADUAL DEVELOPMENT OF SUBTERRANEAN MOVEMENTS 



FAULTS — DOCTRINE OF THE SUDDEN UPHEAVAL OF PARALLEL MOUNTAIN- 

 CHAINS — OBJECTIONS TO THE PROOF OF THE SUDDENNESS OF THE UPHEAVAL, 

 AND THE CONTEMPORANEOUSNESS OF PARALLEL CHAINS — TRAINS OF ACTIVE 

 VOLCANOS NOT PARALLEL AS LARGE TRACTS OF LAND ARE RISING OR SINK- 

 ING SLOWLY, SO NARROW ZONES OF LAND MAY BE PUSHED UP GRADUALLY 

 TO GREAT HEIGHTS — BENDING OF STRATA BY LATERAL PRESSURE — ADEQUACY 

 OF THE VOLCANIC POWER TO EFFECT THIS WITHOUT PAROXYSMAL CONVUL- 

 SIONS. 



mer 



periods, as well as on the power of moving water, geologists 

 have been ever prone to represent Nature as having been 

 prodigal of violence and parsimonious of time. Now, although 

 it is less easy to determine the relative ages of the volcanic 



than 



formations, it is und 



that 



igneous rocks have been produced at all geological periods, or 



and vegetable remains. 



marked by peculiar animal 



commoi 



called trappean have been injected into fissures, and ejected at 

 the surface, both before and during the deposition of the Lau- 



r 



Cambr 



Ma 



New 



formed 



several tertiary groups newer than the chalk, originated in 



succession. Nor 



be referred to the subordinate divisions of each period, such 

 as the Carboniferous, as in the county of Fife, in Scotland 



masses 



