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



is, therefore, obviously of the very first importance towards 

 enabling us to theorize on the seras of the geological disturb- 

 ances. With regard to the greater aggregates constituting for- 

 mations, this investigation has been prosecuted to a certain 

 extent; but very much remains to be done even in this de- 

 partment : and in order to enable us to push the inquiry to 

 its full extent, not only aggregate formations but individual 

 beds should be similarly examined in every case of disturbed 

 strata. We ought in this manner to ascertain the exact limits, 

 and thence to infer the geological asra of the disturbance; — but 

 in what instances has this yet been done? Enough, however, 

 has I conceive been accomplished to authorize the general 

 conclusions enounced in the above article. The disturbances 

 of the transition formations appear to be universal ; they are 

 well exhibited in the coasts of Devonshire and Cornwall, and 

 St. Abbe's Head, Berwickshire. I have, indeed, never seen 

 these rocks exhibited in a single locality, or read any descrip- 

 tion of such, where they did not appear to have suffered the 

 most violent derangements. 



The period of a great part of these disturbances appears 

 to have been antecedent to the formation of the carboniferous 

 formations (although of course the transition rocks must have 

 been affected by the subsequent convulsions which acted on 

 the strata also) ; for we find a want of conformity, and the 

 planes of the transition rocks appear to have been greatly 

 contorted before the application of the planes of the carboni- 

 ferous series of strata upon them. There is, indeed, some de- 

 gree of difficulty in making the requisite observations, because 

 the graywacke rocks have generally a false cleavage, not 

 parallel to the true lines of stratification, which can only be 

 observed by tracing the junction of heterogeneous beds, e.g. 

 graywacke and transition lime, &c. In this manner the non- 

 conformity of the transition rocks of the English lake district, 

 and the superincumbent carboniferous strata of the Cross-fell 

 chain, has been observed. The same non-conformity of the 

 South-Welsh carboniferous and transition strata may be ob- 

 served along the north edge of the coal-field. 



In Somersetshire the junction is altogether connected by 

 the overlying new red sandstone. The Scotch coal-fields 

 have not yet been examined with this view ; nor, as far as I am 

 aware, any of the continental depots. In Ireland the car- 

 boniferous rocks of the Connaught and Leinster coal districts 

 rest unconformably on the' older formations; and a similar po- 

 sition is often noticed in Weaver's excellent Memoir on the 

 South-east of Ireland. 



The 



