MILLSTONE GRIT. I/I 



The variations of the Millstone Grit will be seen from the 

 following divisions noted by IMr. G. H. Morton:' — 



North Flintshire. South Flintshire. 



/ Gwespyr Sandstone I20 Aqueduct Grit 5° 



Cefn-y- I Cherty Sandstone... 250 Upper Sandstone and Shale 100 



Fedw ' Cherty Shale 250 



andstone. \ Lower Sandstone and Con- 



\^ glomerate 5° 



370 feet 450 feet 



Cefn-y- 

 Fedw { 

 Sandstone. 



In the country around Llangollen the beds have been divided 

 as follows by Mr. Morton : "^ — 



Feet. 



/Aqueduct Grit, or Upper Sandstone and Con- 

 glomerate 70"! Millstone 



Upper Shale Zo r Grit. 



Dee Bridge Sandstone 30J 



Lower Shale, with Fireclay and Bands of Lime- 



stone 18 j 



Middle Sandstone 200 ( Yoredale 



Cherty Shale 5°/ Series. 



Lower Sandstone and Conglomerate 2501 



, Sandy Limestone 75/ 



Carboniferous Limestone. 



IMany fossils have been found in the Cefn Sandstones, including 

 the Trilobite Phillipsia. 



In Anglesey the thickness of the Millstone Grit has been estimated 

 at 400 feet. It consists of yellow sandstone and conglomerate, 

 and contains a bed of coal about a yard thick, which has been 

 worked at Glantraeth. 



In Leicestershire the thickness is about 200 feet. The beds 

 consist in the lower part of quartzose conglomerate, seen above the 

 Carboniferous Limestone at Ticknall, and other places ; in the 

 middle, of grits worked at Stanton, INIelbourne and Repton Rocks, for 

 millstones, troughs, and building-purposes ; and in the upper part 

 of grits and shales, which pass by almost insensible gradations into 

 the Coal-measures above. Sections of this passage have been 

 observed near Castle Donnington and Thringstone. 



In Monmouthshire the beds consist of hard sandstone and con- 

 glomerate, with shale partings, and have a thickness of 330 feet. 

 They form the Blorenge ]Mountain, south-west of Abergavenny. In 

 the Forest of Dean the thickness is 470 feet. Mr. E. Wethered 

 states that the rock there in places contains 98 per cent, of silica. 



In South Wales, on the northern margin of the Coal-basin, the Mill- 

 stone Grit forms a continuous band and generally a marked feature, 

 from near Haverfordwest to Pontypool, having at iMerthyr Tydfil a 



' Proc. Liverpool Geol. Soc. vol. iv. 

 ^ Proc. Liverpool Geol. Soc. iii. 174. 



