272 



THE LOWER CARBONIFEROUS ROCKS OF 

 MILL GILL (WENSLEYDALE). 



COSMO JOHNS, M.I.Mech.E., F.G.S. 



Introduction. 

 When the Yorkshire Geological Society made Bainbridge its 

 headquarters for the June meeting, it was only to be expected 

 that the well-known Mill Gill near Askrigg would be visited. 

 To the writer the visit was specially welcome for it enabled him 

 to further renew his acquaintance with sections that he had 

 investigated some four years ago, the results of which are still 

 unpublished, though the conclusions have been the subject of 

 private communications to other workers in Carboniferous 

 Geology. Phillips knew the ground well, though the typical 

 Yoredale Series as described in his ' Mountain Limestone of 

 Yorkshire," is based on a generalised section in which local 

 variations are omitted. Owing to the labours of Dr. Wheelton 

 Hind the fuana of the Yoredale rocks became well known, and 

 Mill Gill with Whitfield Gill received special attention. The 

 state of knowledge at that time did not admit of a determination 

 of the corals with the accuracy now available, and thus the task 

 of correlating the Yoredale Series with some portion of the 

 Carboniferous Limestone Series in areas where a zonal classifi- 

 cation had been adopted, still awaited accomplishment when the 

 writer visited Askrigg in August igo6. From the point where 

 the stream passes under the road, up to the main limestone 

 above Whitfield Scars, an almost continuous series of sections 

 is available, enabling the upper portion of the great Scar 

 Limestone, and the whole of the Yoredales as here developed, to 

 be examined. This present communication is based on observa- 

 tions made during that early investigation, when several days 

 were spent on the sections ; and during the recent visit of the 

 Yorkshire Geological Society. Thanks are due to the President, 

 Prof. Kendall, and the members present, for their valuable 

 and willing services in checking previous records, and making 

 additions. Special attention was paid to those levels where the 

 occurrence of forms known to characterise the Lower Pendleside 

 and Lower Culm rocks had been recorded by Dr. Hind and the 



writer. 



The Succession. 



Making a start in the stream bed at the point where it 

 passes under the Askrigg Road, it is found that for some little 



Naturalist, 



