

THE CARBONIFEROUS SYSTEM 275 



name of Carboniferous slate. This group of beds has derived 

 special importance from its bearing on the Devonian question, and 

 the whole subject is so associated with the name of Jukes that it 

 would be idle to attempt a better exposition of the interest attach- 

 ing to the Carboniferous slate than is contained in Mr. Jukes's 

 own description quoted below. 16 



" If we draw a parallel of latitude through the towns of Ken- 

 mare, Macroom, and Cork, the great development of Carboniferous 

 slate lies wholly south of that line. If we examine the neigh- 

 bourhood of the city of Cork itself, we find the [Upper] Old Red 

 Sandstone with plants in its upper beds, and a very short distance 

 above that we get solid Carboniferous limestone, with some black 

 shales or slates between the two, but not more than 200 or 300 

 feet in thickness. Passing southwards to the mouth of the harbour 

 of Monkstown or Queenstown, and then by Carrigaline and Cool- 

 more, these intermediate black slates or shales thicken to 2000 or 

 3000 feet, still having the Old Red [or Coomhola Beds] below and 

 the Carboniferous limestone above ; but going still farther south 

 by Ringabella to Kin sale, the dark -grey slates and grey grits 

 thicken rapidly to 5000 or 6000 feet, and are nowhere covered by 

 any part of the Carboniferous limestone, though they show here 

 and there highly calcareous bands." 



On Whiddy Island at the head of Bantry Bay there are black 

 shales containing Posidonomya Becheri and P. inembranaceus, the 

 characteristic species of the shales above the limestone, and it is 

 therefore highly probable that the Carboniferous slate is con- 

 temporaneous with the whole of the Carboniferous limestone, the 

 lower and upper parts of that formation passing laterally into 

 shales, just as its middle part does to the northward. We may 

 therefore regard the Carboniferous slate as representing the whole 

 of this limestone and its underlying shale, i.e. strata amounting to 

 a thickness of 2600 feet in the northern part of Ireland ; such, in 

 fact, was Jukes's opinion. 



8. Devon and Cornwall 



This area has been left till the last, because the equivalents of 

 the Avonian Series occurring therein are in many respects similar 

 to those of the south of Ireland and are very different from the 

 typical Avonian of the Bristol and Mendip area, in spite of the 

 close proximity of the two fades. 



Devonshire. The delimitation of the Upper Devonian and 

 Lower Carboniferous rocks in Devonshire has not yet been worked 

 out. The junction-beds have not been specially described since 



