394 ME. G. H. MOETON^ OX THE CARBOISTFEEOTIS [Aug. 1 898, 



map. The names of all the places to which reference is made are 

 derived from the 6-iiich Ordnance map. 



The most important exposure of the Carboniferous Limestone on 

 Little Orme's Head is along the north-western escarpment of the 

 northern range, visible from the parade and the rising ground above 

 Llandudno. Two large quarries are prominent on the steep slope 

 of the hill at Nant-y-Gammer, and both are worked in the Lower 

 Brown Limestone, while the ridges along the top are formed of the 

 lower beds of the lliddle AMiite Limestone. The limestone of both 

 subdivisions dips about 15^ south-east. 



The base of the Lower Brown Limestone is not exposed, 

 but the Caradoc or Bala Beds are seen about -| mile to the south- 

 west, and no doubt occur much nearer the bottom of the hill. 

 The limestone is exposed in an excavation below the lowest of the 

 two quarries, and exhibits the waterworn sides of a large cavern 

 or swallow-hole about 35 yards across, from which the roof has 

 been excavated during quarrying or mining operations. The rock 

 occurs in thick beds, and must be at or very near the base of the 

 Lower Brown Limestone. In the quarries higher up, the limestone 

 occurs in much thinner beds, these being only from 3 to 9 inches 

 thick about the floor of the upper one, but thicker towards the top. 



In the upper quarry, where the limestone is 60 or 70 feet thick, 

 a large portion has been converted into dolomite in a very irregular 

 manner. In some places the dolomite occurs in patches, and in 

 other instances in beds which alternate with the limestone. A bed 

 of limestone often runs against a fault or joint, on the other side of 

 which it has been converted into dolomite. About the top of the 

 quarry the dolomite is from 10 to 20 feet thick, but the thickness 

 varies continuously throughout the exposure. Immediate!}- north 

 of these quarries a small one is worked in the limestone on the 

 roadside, and a fault or fissure about 5 feet in breadth, running 

 north-west or north-north-west through it, contains a filling of 

 dolomite, thus proving that the alteration occurred after the limestone 

 had been faulted and thrown into its present position. 



The colour of the Lower Brown Limestone is dark grey, but it is 

 often partially stained dark red, and is thus easily recognized in 

 walls about the south of Llandudno. The dolomite is of a yellow 

 or buff colour, and is used for rough building-purposes, rockeries, 

 and road-metal. iS'o fossils were seen in either the limestone or 

 the dolomite, which weathers to a brown colour, resembles sand- 

 stone in texture, and disintegrates rapidly. The thickness of the 

 subdivision is about 250 feet. Half a mile east, the Lower Brown 

 Limestone is again exposed at the bottom of Mynydd Pentre with 

 the succeeding subdivision over it. 



The Middle White Limestone occurs above the Lower 

 Brown Limestone along the crest of the hill at Nant-y-Garamer, 

 and dips to the south-east. It is well exposed above Bodafon and 

 at the ' Old Tower,' where the surface begins to descend with the 

 dip, and the eroded beds occur over a considerable area. Lower 



