D. C. Davics.— The Millstone Grit of North Wales. 73 



Fio. 8.— Section of Millstone Grit, with intcrstratifiod limestones, 3i niilcH west of 



Mold, Flintshire. 

 Corncl-fcdw. Bryngwyn. Pcn-y-mynydd. 



1. Main body of Carboniferous Limestone. 



2. Massive reddish white, dark red, and yellowish sandstones 



3. Massive arenaceous limestone ... 



4. Clays, limestones, and yellowish sandy beds 

 7. Massive limestones 



5. Various purplish calcareous sandstones, with encrinites and coralline limestones 



6. Massive crystalline white sandstones, with occasional layers of pebbles, and fucoid 



markings between the beds ,„ 



294 



(Measurements to be taken as approximately correct.) 



Passing on to Trevor, three miles east of Llangollen, we have 

 the upper beds made up (as shown in the accompanying Trevor 

 section) of compact sandstone, with crystals of felspar, ranging in 

 texture from a coarse friable conglomerate to a fine-grained sand- 

 stone. This character it maintains (omitting the friable conglomerate) 

 to Mold, in Flintshire, where it forms the topmost sandstone of the 

 Mold section (see Woodcut, Fig. 8). The basement beds at the two 

 extremities of the formation differ considerably : at the southern 

 end they are red and purplish sandstones ; at the northern termi- 

 nation, on the Ormes Head, we find the main body of the limestone 

 immediately succeeded by a succession of cherty beds. The middle 

 beds preserve their calcareous character throughout the entire area, 

 becoming more decidedly calcareous in their passage northwards; for 

 example, taking three points at about equal distances, we have — 



(North.) 



(South.) At Sweeney (1 mile). 

 Calcareous sandstones, 

 with occasional thin 

 layers of limestone. 

 Total thickness » ngQft 

 of each section. ) 



Trevor (15 miles). 

 1ft. 6in. limestone, 16ft. 

 cherty ditto, calcareous 

 sandstones. 



294ft. 



Mold (30 miles). 

 About 120ft. lime- 

 stone. 



2944ft. 



So rapid is the increase of calcareous matter, in the last fifteen 

 miles, that it is difficult, when looking at the Mold section, to say 

 whether we have, as shown on the Government Survey maps. Mill- 

 stone Grit with bands of limestone, or, limestone interstratified with 

 beds of grit. 



fTo be concluded in our next Number.) 



