the Formatim of the superficial Pari of the dole. 457 



inatlons, there being no two countries in which the order of sue- 

 eession is found to agree ; and a recent examination, by Rai- 

 nier, of the very district in which the Professor of Freyburg laid 

 down the law of succession for the whole globe, is said to have 

 shown that Werner's descriptions do not even agree with the 

 actual order of succession in which the rocks of that district are 

 arranged. 



Granite, porphyry, sienite, green-stone and basalt pass by 

 such insensible gradations into each other, and into rocks known 

 to be volcanic, that the probability of their having a similar 

 origin can scarcely be denied. And if the internal fires that 

 have acted successively on the surface of the globe were of vast 

 extent, as the remaining craters indicate, they may aiso in nu- 

 merous instances have melted or softened pre-existing rocks and 

 strata, and occasioned the bending and contortions of the strata, 

 and other phaenomena on which the theory of Dr. Hutton was 

 founded. The defect of that theory consists, 1 conceive, in ex- 

 tending the operation of this cause furtlier than existing appear- 

 ances will support. 



Were we to admit that rocks are local formations produced 

 by successive igneous and aqueous eruptions forced through, 

 craters and fissures of the surface, these, with subsequent eleva- 

 tions and subsidences of the surface, might be sufficient to ex- 

 plain all the various phaenomena which the position, contortion, 

 succession, and alternation of rocks and strata present to our 

 notice. In some situations granite mountains are covered with 

 a series of schistose rocks, to which succeeds the mountain 

 limestone, and on this are laid the sandstones of the coal forma- 

 tion. In other instances these sandstones rest immediately on 

 granite, without the intervention of schistose rocks. Here then 

 we may suppose that no eruptions of matter took place between 

 the formation of the granite and the sandstone ; while in other 

 situations a succession of formations had produced all the inter- 

 mediate rocks. In some countries the eruption of matter which 

 formed granite, after ceasing for ages had again taken place, and 

 thus sometimes we find granite covering rocks to which it is 

 most frequently subjacent. To a like cause may we ascribe the 

 occasional appearance of beds similar to the lower rocks alter- 

 nating with or appearing in the upper strata. The siliceous and 

 calcareous solutions in a state of tranquillity might also envelop 

 the fragments and sand from pre-existing rocks, and form the 

 various breccias and aggregated sandstones. Saline and bitu- 

 minous matter may also have been thrown up ia dotac'ied lakes, 

 and subsequently consolidated, as in the pitch-lake in the Island 

 of Trinidad. The local formation of beds of trap alternating 

 with other rocks has before been alluded to^ and the graduation 



of 



