278 GEOLOaiCAL NOTES FOR A VISIT TO ROTHLEY CRAG. 



limestones, and rare coals of the Yoredale series. It was 

 especially natural when one remembers that the grits of these 

 crags are much coarser than those of any beds above them in 

 the higher Carboniferous deposits, and tally exactly with all 

 preconceived notions as to the characters proper to typical 

 Millstone Grit. That marine fossils were found in beds above 

 the crag-forming strata was not held to be in any way incon- 

 sistent with this classification, since not very dissimilar fossils 

 had been found in more than one marine band in the un- 

 doubted Millstone Grit in the more southern counties. It 

 must not be forgotten also that the bands of limestone which 

 are now such invaluable factors in the correlation of the 

 Carboniferous beds had then been carefully distinguished, and 

 to some extent mapped, only in the lead-mining districts of 

 Alston, AUenheads, and Weardale, all many miles away. It 

 was the patient following of the outcrops of the most remark- 

 able of these limestones from these districts northward, which, 

 after many years' delightful labour, enabled one to rectify the 

 erroneous inferences which had been arrived at in the absence 

 of sufficiently accurate data, and showed that the strata from 

 the " Great Limestone " upwards as far as and including the 

 " Felltop Limestone," belonged to the Carboniferous Lime- 

 stone series, and that, in mid-Northumberland, the true 

 Millstone Grit (/.<?., the beds between the Limestone series 

 and the Coal Measures) was represented by a comparatively 

 insignificant set of sandstones and shales with very occasional 

 coal seams of no great value and no limestone — altogether of 

 quite small thickness, and devoid for the most part of that 

 character of coarseness of grain which had usually been 

 regarded as essential to that division. I must hasten to say 

 that as soon as the stratigraphical evidence was placed before 

 Sir Walter Trevelyan he not only cheerfully adopted the 

 conclusions to which it led, but helped personally in working 

 out their details. Rothley Crag is thus a classic spot as 

 regards Northumbrian geology, and deserves notice as such ; 

 it affords besides a most extensive view over a considerable 

 extent of interesting country. From its summit the eye ranges 



