28o GEOLOGICAL NOTES FOR A VISIT TO EOTHLEY CRAG. 



Lower Bernician. 



Many hundreds of feet of sandstones, shales, thin limestones, and 

 coals, with at its base a very thick crag-and-hill-making set of 

 sandstones (often coarse) known as the Fell Sandstones, which 

 is placed by the Geological Survey at the top of the 



TUEDIAN. 



Many hundreds of feet of sandstones, shales, and thin more or less 

 argillaceous limestones (Cement Stone), with at the base an 

 irregular deposit of pebbly conglomerate which is usually 

 known as the 



Basement Beds (of the Carboniferous System). 



(N.B. The entire thickness of the Bernician series at the latitude of 

 Rothley is probably between 6,000 and 7) 000 feet ; that of the beds 

 between the Felltop Limestone and the Great Limestone is here about 

 1,300 feet, whereas the same group south of the River Tyne is not more 

 than 300 feet in many places). 



It was in 1878 that I gave the name "Inghoe Grits "to the 

 coarse grits which form the marked feature first seen between 

 the Tyne and Wansbeck (as at Inghoe and Shafthoe Crags), 

 and continued to Rothley between the Wansbeck and Coquet. 

 Rothley Crag is in fact the northermost of the bolder escarp- 

 ments due to these rocks. At the three places mentioned the 

 nature of the stone is identical. It consists of thick lenticular- 

 shaped accumulations of angular grains of glass-clear quartz 

 held together in a cement, much of which is more or less com- 

 pletely decomposed felspar. In this matrix are irregularly 

 distributed pebbles of vein quartz, more or less opaque and 

 milky, and often perfectly rounded and waterworn. The 

 rock, where these pebbles are numerous, thus becomes a true 

 conglomerate or compacted shingle-bed, which must have 

 been deposited near shore. It would obviously help one to 

 re-construct the physical geography of the district at the time 

 of its formation if one could with any degree of certainty trace 

 these rolled pebbles to the parent mass from which they were 

 originally torn. They are frequently over an inch in diameter, 

 though usually smaller, so that the distance which they 

 travelled from can scarcely have been very great, and they 

 are generally accompanied by a fair quantity of small but 



