420 SKETCH TOWARDS A 



constitute the "primary" ones of its present condition. 

 In the former sketch of revolutions, being a portion 

 only of a General Theory, this was enumerated as a 

 third mode of the Earth, in conformity to the narrow 

 limits of that view. With the antient geologists, it 

 has been termed primitive, and, under the latest opi- 

 nions, primary. The philosophical geologist will judge 

 of the propriety of a far other place, at least, though 

 he should not admit the whole of the present views. 



I must not, however, conclude respecting this con- 

 dition, without expressing a doubt, which may possibly 

 be a very serious blank in the Theory of the Earth. I 

 do not think that our knowledge of the primary strata, 

 correct as we have been accustomed to believe it, is 

 sufficient to prove that it is the produce of one revo- 

 lution ; while the antiquity of these, and the numerous 

 changes to which they have been subjected, may well 

 render them obscure. If I formerly suggested this 

 suspicion, hinting at some facts which I could not ex- 

 plain on the present theory, I may here add, that the 

 greatest difficulty I have found, is in trying to recon- 

 cile the Chlorite series of Scotland with any condition 

 so simple as that which is here examined. 



How far such facts as this may be supported by pa- 

 rallel ones, I cannot foresee, and geologists have not 

 sought, because they had either no theory or a false 

 one. If partial, it may not prove of much import, nor 

 materially disturb the general theory : but if it should 

 be widely confirmed, it may prove that our primary 

 strata are the produce of two, if not of more revolu- 

 tions, and therefore include two classes of rocks, or two 

 conditions of the earth, at least. Yet having no other 

 reasons than these, I leave this as a hint for future 

 geologists ; as I need not say how a proof of the fact 

 might possibly modify the general theory of numerical 

 successions as here given. 



