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GEOLOGY (continued).


The following fossils have been observed in the upper-part of this sub-division of the limestones at Tan-y-alit, near Meliden, and at Tyn-y-allt, Prestatyn Spirifera glabra, Spirifera pinguis, Terebratula sacculus, Produetus aculeatus, Orthis resupinata. In the most Southern of the quarries in Coed yr E-sgob (Bishop's Wood) have been found, Cladodus mirabilis (teeth of) Goniatites sphoericus, Orthis resupinata, Produetus semireliculatus, Spirifera trigonalis, h cusipata, „ glabra. At the Gop Hill and the quarry at Axton, Newmarket, a large number of perfect and varied fossils have been found, chiefly iu the Upper Grey Limestone, In the Black Lime- stone base near Gulgrave the following species were obtained Aviculopeeten, Pap- yraceus, Productus Scabriculus, Rhyncbon- iolia Pleurodon. MILLSTONE GBIT.-Scarcely any part of Britain shows a more remarkable development of chert than that which overlies the Carboni- ferous Limestone in North Flintshire. From the sea near Gronant it runs through Llanasa, Trelogan, Holywell, and Halkin Mountain, with a full thickness of 350ft. and consisting, with the exception of thin shaly partings, and a few shale-bands, of almost pure silica. The ■chert is probably a silicious sediment of extreme firmness well stratified, evenly laminiated, and by a gradual lithological change, it passes horizontally into a fine grained quarzose sandstone, with bands of ichert, and finally into a quartz grit with quartz pebbles, in which chert-bands are -•rquite abundant. Numerous pieces of bands may be picked "out of some old mining hillocks above Terfyn and near the Voelnant Telegraph Station. The higher beds of the chert are generally fblack, thin-bedded with partings of hard and brittle laminated shales. They are best seen in a quarry at Peotre near Gronant, where e in "they are chipped into cube blocks for use in -the Potteries. -The workings of the Talacre mine are prin- cipally in the Chert Beds. The vein is filled with calc-spar, and a great deposit of loose white sand, derived from the decomposition of a siiicio-calcareous vein Stuff that is com- mon in these beds. The ore is principally zinc blende. LOWEU COAL MEASURES. —Three trials have been made to reach the rock between Talar- goch and Prestatyn, but all were abandoned before penetrating the great depth of drift. Half way between Meliden and Prestatyn, at a distance of 150 yards from the limestone slope of Carreg-y-Fran, the drift consisted of the following beds, all of which are glacial:— Clay and stones 21 feet, red clay 12, gravel 27, dark stiff clay 27, clean sand 36, stony clay and mud 48, moist sand (not bottomed) 88+. The other trials were close to Graig Fawr; and 200 yards from Tyn-yr-Allt Prestatyn. A boring was tried close to Prestatyn station (52 chains west) and reached a depth of 675 feet, by the late Mr Gilderoy. The strata, below the glacial deposits consisted of red sandstone, white sandstone, and red and white marls. One of the workmen stated that rock was reached at about 70 feet. Professer Hull in his evidence before the Royal Coal Commission in 1871, stated that coal measures of some sort were found. Mons Moissenet, in his Annales des Minesa published in Paris in 1857, states that a fine red sandstone, presenting all the characters of the Bunter sandstone, was found in one of the workings of Talargoch mine at a depth of 100 yards, but no confirmation of this has been forthcoming. A narrow strip of the newer Carboniferous rocks runs from Prestatyn by Meliden and Dyserth up the Vale of Clwyd, and separates the Bunter sandstone from the older Carboni- ferous Limestone and Wenlock Shale. The three principal veins of the Talargoch Mine run about S.W. to N.E. and pass from the white limestone through the black lime- stone. They are then lost to view in a great body of black shales with thin sandstones and coal-seams, which succeeding immediately to the black limestone without the interven- tion of the Chert Beds, must clearly be intro- duced by a large fault. The position of this fault was proved in the Mostvn Shaft, about 100 yards south of Meliden Church, at a depth of 190 yards. The following section was noticed in 1878 in a cross cut from the south joint at 180 yards depth metal (or shale) 10 feet, coal 5 inches, splintery metal 1ft. 2, coal 8 inches, metal 2ft. (To be continued.)







North Wales Junior League.

Prestatyn v. Denbigh.