CONSISTENCY OF GEOLOGY WITH SACRED HISTORY. 427 



been cut through, by those causes which formed the present valleys, 

 they are then obviously older than the valleys, and where these cur- 

 rents have flowed into valleys, beds of rivers, &c. they are as evi- 

 dently of a more recent date. 



Although the formation of these volcanic regions was anterior to 

 the records of history, it was, evidently, in the most recent portions, 

 posterior to the existence of organized beings, which are found im- 

 bedded in the volcanic tufa. 



The recent researches of Humboldt, " have greatly extended our 

 knowledge of the volcanic tracts of our globe ; he has shown the 

 whole country round the Caspian to be a vast district of this nature, 

 a "pays cratere," exactly resembling, in its general outlines, the tele- 

 scopic appearance of the moon ; he has also pointed out another great 

 ■seat of volcanic action, the chain of Thion Chou, south of the Altai, 

 and running about 42° lat. N. and between 70° and 80° long. E. of 

 London. This vast ignigenous district extends over two thousand 

 five hundred square leagues, and being generally remote from every 

 sea, shows that marine contiguit}^, although a common, is by no means 

 an indispensable concomitant of volcanic action."* 



For our purpose, it is not necessary to go any farther into detail, 

 with respect to this class of rocks. All that is true of modern erup- 

 tions from active volcanos, considered as proofs of succession in geo- 

 logical events, is true in the present case. Every thing was occasion- 

 ally covered by the currents that issued from the ancient volcanos, and 

 there is no reason to doubt, that, as happens in connexion with mod- 

 ern volcanic convulsions, destructive earthquakes preceded and attend- 

 ed their eruptions. 



It is not our purpose, on this occasion, to enter into the considera- 

 tion of the theory of volcanos. It is undoubtedly obscure, and at- 

 tended with many difficulties, especially in the extent to which the 

 view of igneous action is carried by most of the geologists of the 

 present day. "It is impossible, (says Conybeare,) to propose, as ex- 

 planatory of volcanic phenomena, any probable theory, which does 

 not, at the same time, embrace the entire structure of the globe, in 

 all its generality."! 



3. Ancient Rocks of Igneous Origin. 



With respect to the extent of this class of rocks, there has been 

 great diversity of opinion. 



* Discourse of Prof. Conybeare on Geology, at Oxford University, 1832, 

 t Discourse at Oxford, 1832. 



