Vol. 55.] THE CRAVEN DISTRICT OF YORKSHIEE. 357 



intervening depressions are filled with shales, but the sections are 

 rather poor. 



The structure of the middle and lowermost Upper Devonian 

 Limestones of the Torquay area has frequently been the subject 

 of remark. A cursory inspection of them some years ago gave 

 evidence of the same kind of features as those which I have 

 described as occurring elsewhere in knolls. I have already alluded 

 to Mr. Wethered's remarks on these rocks, and would here quote 

 a suggestive passage from Mr. Ussher's paper on the Devonian 

 rocks of South Devon ^ : — ' A part of the Barton limestone is a 

 coral-breccia recemented; and in one nearly vertical fissure or 

 fault the fragments also appear rolled. Whether this phenomenon 

 is due to surf-talus banked on a mass of coral-growth or not, I 

 leave to the judgment of those better qualified to form an opinion.' 



On the Continent I have seen what I take to be knoll-structure 

 in the Ordovician Lej^tcena-limestones of Dalecarlia, and in the 

 Devonian limestones of Koneprus in Bohemia. The Leptcena- 

 limestone exhibits all the features which I have described as charac- 

 teristic of knoll-structure, and it would be tedious to repeat them ; 

 and the same may be remarked of the limestone of Koneprus. A 

 very significant fact is the inclusion in the Lepfccna-limestone of 

 Boda of apparent pebbles of shale, which, however, belong to beds 

 newer than the Leptcena-limQstoiiQ, indicating the occurrence of 

 complex earth-movements here. In the case of the Leptcena- 

 limestone jS'athorst has brought forward evidence that it is a special 

 condition of a thin unfossiliferous limestone — the Klingkalk,^ while 

 the thick knoll of Koneprus is represented nearly all the way 

 round the Bohemian basin by a thin band of grey or white horny 

 limestone. 



I would once more emphasize the fact that all these knoll- shaped 

 structures occur in regions where the rocks have been subjected to 

 considerable erogenic movements. 



IX. Concluding Remarks. 



I have attempted to show that knoU-structure is produced by 

 orogenic movements. In so doing, I have admitted that my exami- 

 nation of the only tj^pical ' knolls' (according to Mr.Tiddeman) that I 

 have seen did not furnish much direct information in support of my 

 views, and I have tried to prove that there is a similarity of struc- 

 ture, indicating community of origin, between the typical knolls 

 and other knoll-like masses which I have endeavoured to explain as 

 due to orogenic movements. 



I must frankly admit that my views are contrary to those of 

 well-known writers. The limestones of Keisley, Devon, and 

 Dalecarlia, as well as those of Craven, have been elsewhere ascribed 

 to processes not differing in a marked degree from those suggested 



1 Qaart. Journ. Geol. Soc. vol. xlvi (1890) p. 503. 



' Geol. Foren. i Stockh. Forhandl. vol. vii (1885) p. 559. 



