264 PROF. E. HULL ON THE GEOLOGICAL RELATIONS 



of Baggy Point and Marwood, 5200 feet. In all of Devonian beds 

 proper, 9600 feet. 



(c) From the CaeuUcea- and plant-beds to the flinty calcareous 

 slates of Barnstaple, 2200 feet. 



Absence of the Middle and Lower Devonian Series in Ireland. 



After the description above given of the Middle and Lower 

 Devonian beds of North Devon, it may be asked, Where is such a 

 group to be found in the South of Ireland ? 



According to the views I entertain, they are not represented at 

 all. As I have already shown, the Old Eed Conglomerate of the 

 South of Ireland has no immediate predecessor in the formations of 

 that country. The hiatus and unconformity which are so marked 

 between the Glengariff beds on the one hand and the Old Red or 

 Lower Carboniferous beds on the other * show that certain strata 

 are absent over this area ; and if the correlatiou I have indicated 

 above between the Devonshire and Irish sections be correct, then 

 it follows that the Middle and Lower Devonian beds exactly occupy 

 the place of tlu missing strata in the South of Ireland. Any attempt 

 therefore to correlate these beds with the Glengariff or Dingle series 

 appears to me an error ; and it is not till we reach the basement- 

 beds of the whole series of North Devon, viz. the Poreland grits 

 and slates, that we have any real representatives of the Glengariff 

 beds, which, on grounds already stated, I consider to be of Upper 

 Silurian age t. 



The view which I now venture to offer for explaining the rela- 

 tions of the Devonian series to the formations of the South of Ire- 

 land seems to meet the difficulties which have hitherto beset this 

 problem J. I have already shown that in the South of Ireland the 

 succession of the strata was interrupted after the formation of the 

 Glengariff or Dingle beds. Up to this, from the base of the Upper 

 Silurian series, throughout the Wenlock, Ludlow, and Gengariff 

 stages, deposition went on uninterruptedly; and then came cessa- 

 tion of deposition, elevation of the sea-bed, and denudation. Every- 

 where between the Glengariff beds and those which succeed them, 

 whether Old Eed Conglomerate, Kiltorcan flags, or Lower Carbo- 

 niferous grits and slates, there occurs a breah in succession of strata, 

 an hiatus, indicative of land-conditions and the absence of certain 

 strata for which we are obliged to look elsewhere. Now, as all the 

 beds from the Carboniferous Limestone to the Pickwell-Down sand- 

 stone inclusive, are clearly represented in the South of Ireland by 

 the Carboniferous Limestone, the Carboniferous Slate, the Coomhola 

 Grit, and the Old Eed Sandstone, it is clear that the Middle and 

 Lower Devonian beds of Devonshire are in reality the missing 

 strata. But before pursuing this subject further I wish to show 



* The relations of these beds are iUustrated by a diagrammatic plan and sections 

 in my paper above quoted, p. 713. 



t Ibid. pp. 703, 715-718, &c. 



I These views were first briefly sketched out in a paper published in the 

 * Geological Magazine,' Dec. 1878, and have received the approval of Mr. A. 

 Champernowne, F.Gr.S., in the Geol. Mag., March 1879. 



