402 Rev. W. D. Conybeare on the Phenomena of Geology 



to have been of ancient volcanic origin : the greenstone and 

 other trap rocks are now almost universally thus considered ; 

 and the granitic rocks have so many points of analogy with 

 these, that they can scarcely be referred to a different origin. 



Observation. — It would be a useless expense of space here 

 to enter into the detail of the phenomena thus referred to, as 

 they are universally familiar, and the inferences from them 

 generally allowed. 



IV. The disturbances which the strata appear to have suf- 

 fered subsequently to their original formation (as shown by 

 faults, the inclined and contorted positions of beds which 

 must have been deposited horizontally, &c.) prove that they 

 must have undergone very extensive mechanical dislocation. 



Observation. — Of course it is natural to look to this mecha- 

 nical dislocation as the proximate cause of the elevation of the 

 continents, by which they have emerged from their original 

 subaqueous position (sect. I.); and further, we seem in the vol- 

 canic agency indicated in No. II., to find a cause adequate to 

 produce this dislocation. Of course we must conceive this 

 volcanic agency to have affected the surface with greater or 

 less violence at different periods, in proportion as we find the 

 strata more or less dislocated at those periods. 



V. In all the countries hitherto examined, we find these 

 dislocations affecting the oldest formations in the most violent 

 manner, and to a degree beyond all comparison greater than 

 those of newer deposition. Thus we find the transition for- 

 mations universally and most violently disturbed ; the carbo- 

 niferous series very generally and very greatly so ; the new 

 red sandstone and all the superior rocks in most countries 

 comparatively very little deranged ; — although faults, &c. still 

 occur, and prove that the same disturbing causes were still 

 in action, though with an energy much diminished. In parti- 

 cular localities however, (but these of very limited extent com- 

 pared with the entire surfaces of our continents, as far, that is, 

 as hitherto explored,) these disturbances extend even to the 

 tertiary formations. Jt generally* appears that these localities 

 are in the neighbourhood of the most lofty mountain chains : it 

 seems indeed established, that the height of these chains bears 

 a general proportion to the geological period during which 



* I say ' generally,' because our own Southern coast in the Isle of Wight 

 and Dorset, presents an example of exception, namely, of violent convul- 

 sions having affected the chalk and lowest tertiary beds without producing 

 any mountain chain. I stated originally the above law as to the height of 

 mountain chains, with relation to the periods of disturbance, in the Num- 

 ber of the Annals for January 1823, pp. 3 and 4, exemplifying it with re- 

 ference to the Alps and Pyrenees. I believe the idea was at that time 

 original ; it seems since to have occurred also to Elie de Beaumont. 



the 



