1819.] Greenough on the First Principles of Geology. 371 



Of these arguments, the only one which appears to me to pos- 

 sess weight is the last. Before we can be in a capacity to judge 

 whether Pallas's cause be inadequate or not, it would be requi- 

 site to know the size of the islands alleged to have started out of 

 the ocean, and the depth of the ocean in that part before their 

 appearance. 



Our author is as little disposed to admit the explanation of the 

 origin of the debacle given by Sir James Hall ; namely, the 

 elevation of our present continents by explosions. Such an 

 elevation would doubtless have thrown the ocean into a violent 

 agitation ; but how this agitation could have excavated the 

 valleys, and covered with alluvial deposits the very continents 

 which were elevated above its action, is a question which does 

 not admit of an easy solution. 



Our author is of opinion that the universal diffusion of alluvial 

 sand, gravel, Sec. demonstrates that a universal inundation has 

 formerly taken place. That these alluvial deposits abound in 

 low-lying countries is a fact that admits of no dispute ; but I am 

 not aware of any evidence of the existence of these substances 

 at great heights above the level of the sea. If any confidence 

 can be placed in Humboldt's observations, no mountain exists 

 in America above the height of 10,000 feet which is not volcanic. 

 The Alps contain no alluvial deposits at great heights. The 

 same thing may be said of every range of primitive mountains 

 hitherto examined ; unless we were to consider small-grained 

 granite and granular quartz as alluvial deposits. These indeed 

 are so connected with the other rocks, that if their alluvial 

 nature were admitted, that of almost all other rocks would follow 

 as a consequence. But as our author does not consider the 

 calcareous and other rocks which abound in fossils to have been 

 formed by the debacle, but to have existed before that period ; 

 neither can he admit the small-grained granite, granular quartz, 

 &c. to have been owing to his debacle. Of course his argument 

 for the universal distribution of alluvial debris remains unsup- 

 ported. 



The universality of the deluge, he thinks likewise demonstrated 

 by the universal recurrence of mountains and valleys. And 

 certainly if it be admitted that valleys were excavated by the 

 deluge, this argument is conclusive. 



The figure of the surface hardly ever corresponds with the 

 disposition of the strata and veins beneath it. This shows that 

 the figure of the surface has been altered ; but whether by a 

 debacle, or by the gradual action of the weather, Sec. is not so 

 clear. 



Our author enters into a disquisition respecting the structure 

 of the surface of the globe. He thinks that towards the equator 

 there is a belt of mountain that encircles the earth ; while both 

 W the north and south, these high grounds are bounded bv low 



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