BaJcewelVs Introduction to Geology 357 



Chapters 5 and 6., On the Rocks generally denominated Pri- 

 mary. This class Mr. Bakewell limits to granite, gneiss, and 

 mica slate, and the rocks which are commonly associated with 

 or imbedded in them. The three former rocks he regards as 

 merely modes of the same substances, being essentially com- 

 posed of the same earths, but different circumstances attend- 

 ing their formation have disposed them to assume a granitic 

 structure in one part, and in another to separate into laminae, 

 or to take a slaty form. The indications of the present exist- 

 ence of subterranean fire beneath the granite of the Alps 

 and of Auvergne in France, and, according to Humboldt, in 

 the Andes, would, our author observes, render it probable 

 that these rocks are of igneous origin ; and the near connec- 

 tion there appears to exist between granite and other rocks 

 allied to volcanic rocks, tends to confirm this opinion. The 

 granite of the Alps, Mr. Bakewell states, rises in nearly vertical 

 beds, which have been elevated, together with the secondary 

 strata, after the formation of the latter; whereas, in some 

 parts of England, the granite and the slate associated with it, 

 though rising in elevated beds like those of the Alps, are 

 covered by horizontal secondary strata, which must have been 

 deposited after the elevation of the primary beds. Hence Mr. 

 Bakewell infers that the granite of England is more ancient 

 than that of the Alps. Two original sections are given ; one ex- 

 plaining the structure of the Alps, and the other the structure 

 of the granitic rocks and the secondary strata at Charnwood 

 Forest, in Leicestershire, which will enable the reader to 

 judge of the accuracy of the inference respecting their dif- 

 ferent ages. 



Chapter 7., OnTransition Rocks, or the lowest rocks in which 

 organic remains are found. Mr. Bakewell observes that foreign 

 geologists have not unfrequently classed the upper secondary 

 strata with transition rocks, owing to the highly indurated 

 and crystalline state in which the secondary strata occur, 

 particularly in the Alps. Hence erroneous accounts have 

 been given of the bones of vertebrated animals in transition 

 rocks; whereas the rocks in which they are found are not 

 more ancient than the English lias and oolite. Some inte- 

 resting observations on the conformable transition rocks will 

 be found at the end of this chapter. 



Chapter 8., On the Regular Coal Formation ; chapter 9., On 

 Unconformable Rocks of Porphyry, Trap, and Basalt ; and 

 chapter 10., A Retrospective View of Geological Facts, contain 

 many important illustrations of English geology ; and, in the 

 chapter on the coal strata, there are some observations on the 

 search for coal in situations beyond the limits of the present 



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