244 Maiv— Distribution of White Clays and Sands, 



are layers of very black carbonaceous earth. Some of the white 

 sand-beds contain thin layers of small white pebbles, about the size of 

 a pea, which appear to have been derived from the Millstone Gl-rit : 

 on the west side of the section the strata are nearly level, but at a 

 very short distance to the east, they dip at a high angle. 



There is a curious arrangement towards the bottom of the Sand- 

 pit, in which the overlying inclined beds are cut off suddenly against 

 some more level strata under them ; the whole of the strata are also 

 full of slight dislocations, faults, and slips, which irregularities 

 appear to have been produced by restricted movements within a 

 small area, and are disposed as though the beds had been gradually 

 lowered after their deposition into the Limestone cavity during its 

 slow excavation. 



At Craig Vraddoc, between Bwlch Farm and Nannerch, on the 

 southern margin of the Mountain Limestone range of Flintshire, 

 similar sand is also found of a character different from that of the 

 Grlacial drift of the neighbourhood, but I had not an opportunity of 

 examining the locality, or ascertaining the position of the beds. 



Two or three cavities in the Mountain Limestone have been partly 

 emptied of sand and clay at Ty Coe, near Fridd Grarreg Wen, If 

 miles due north of Caerwys. One that has been abandoned for 

 some time appears to be about 150 feet in diameter ; I was informed 

 that it contained, with the sand-beds, a considerable proportion of 

 white clays, which were sufficiently tough for the manufacture of 

 tobacco pipes. I also observed a small exposure of dark laminated 

 clay strata near the circumference of the pocket, dippiag at a steep 

 angle towards its centre. 



A little to the south-east of Langynhafal, in the vale of Clwyd, 

 an adit driven for the purpose of working Haematite, exposed a 

 deposit of dark laminated clay, filling up a fissure in the Mountain 

 Limestone, of the same character as the clays on Holywell and 

 Halkin Mountains, and in mineral aspect closely resembling some of 

 the Eocene Clays of Dorsetshire, and the Miocene beds of Bovey 

 Tracey, in Devonshire. 



Another example in North Wales, of which I have obtained a 

 section (Fig. 4) occurs at Pant du, near Llanferris, Denbighshire, 

 five miles to the south-west of Mold, at an altitude of about 900 

 feet above the sea. It appears to be a lodgment that has been 

 protected from denudation in the angle of a sort of amphitheatre of 

 Mountain Limestone rocks, one side being open to the main valley. 

 The clay has been worked for pottery purposes from a shaft sunk 

 into it seventy-five feet deep. The upper five feet is through lime- 

 stone debris and drift, succeeded by a mass of tough white clay, the 

 base of which was not reached, and consequently the position of the 

 fundamental limestone is uncertain. A head driven from the bottom 

 of the shaft towards the Mountain Limestone escarpment, intersected 

 horizontally 21 feet of white clay, 84 feet of soft chert breccia, 

 similar to that on the Great Ormes Head (described in Geological 

 Magazine for May, 1865), and 27 feet of black laminated Clay, the 

 limit of which was not reached. All these beds dipped at a high 



