422 SKETCH TOWARDS A 



strata. And as the earlier ones must have been ex- 

 posed to its influence most completely, from being re- 

 peatedly subjected to it, under successive revolutions, 

 it is therefore inferred that they originally resembled 

 the most recent secondary strata; as they, and the 

 surface of any or every antiejit earth with them, must 

 have been affected by all the changes of waste and mo- 

 tion which our own is now undergoing. 



I have already shown the difficulty of discovering 

 what rocks were forming beneath the ocean in this 

 seventh Earth, while the preparations for the coal 

 strata were proceeding on its surface. And this forms 

 the first serious defect in a Theory of the Earth. I 

 cannot pretend to supply it: for the first time, geolo- 

 gists have been told that it exists ; and the science 

 claims their exertions to remove this blot, since it lies 

 within that portion of the history of the globe which 

 is amenable to investigation. 



It requires a fourth revolution to depress the now 

 existing and carboniferous strata, so that the superior 

 ones, which are oceanic, may be produced. If I speak 

 of depression, here, while, in all other cases of revolu- 

 tions, it is on elevations that I have dwelt, this is, 

 merely, because it is the only result, in this case, as yet 

 demonstrable. But we cannot conceive an act of de- 

 pression, without some corresponding elevation: while, 

 that we cannot demonstrate this also, in any rocks yet 

 examined, leaves a second blot in a Theory of the 

 Earth. And thus, although there is hei?e implied an 

 eighth condition, during which the submarine strata 

 superior to the coal were in the act of being deposited, 

 we can even less conjecture its nature. 



In the twenty-first chapter, I have spoken of the 

 elevation of all the secondary strata, as succeeding to 

 the depression of th'e coal; thus assigning but one fur- 



