Vol. 54.] LIMESTONE OE THE COUNTRY AROTJND LLANDUDNO. 391 



The limestone forming the ridge (on which the Telegraph stands) 

 a little to the north of the quarries is on the opposite side of the 

 fault and lode shown on the map. This fault is the axis of a 

 synclinal, for the beds in the ridge dip 20" south, and are higher 

 than those exposed in the quarries. The limestone occurs in thicker 

 beds, and contains pink sandy shales, while those of the usual black 

 colour are less frequent. In many places it has been altered into 

 dolomite, while in others it retains its ordinary appearance, and 

 contains the usual fossils, the most common being Productus gi- 

 ganteus. The dolomite occurs in irregular beds, lenticular masses, 

 dykes, and veins, and the alteration seems confined to the limestone 

 in the vicinity of the lodes. Chert is of common occurrence, filling 

 fissures, and forming concretions around Productus giganteus. The 

 chert is most conspicuous near mineral veins, but it does not occur 

 in anything like such large masses as the dolomite. 



There is another fault about 100 yards north of the Telegraph, 

 running nearly due east and west, as shown in the map (fig. 2, p. 386). 

 It is evidently a mineral vein, and must have been worked many 

 years ago, for there are traces of buildings, washing-floors, and 

 excavations along its course. South of the fault on the upcast side 

 there is a cliff nearly 40 feet high, and a more gradual ascent for 

 100 feet higher to the site of the Telegraph. The limestone forming 

 the cliff' occurs in thick beds, dips 32° W.K.W., is much weathered, 

 and traversed by several fissures which seem to have been excavated 

 by miners in search of ore. J^orth of the fault the lower beds of the 

 subdivision occur, and there are indications of the Middle White 

 Limestone cropping up along that side of the fault. ■ 



The thickness of the Upper Grey Limestone is estimated at about 

 200 feet on Great Orme's Head, the highest beds having been 

 denuded. It was found impossible, however, to measure this: 

 limestone exactly, on account of its occurrence in the depression: 

 described, and the uncertain influence of the faults and lodes which 

 could not be separately indicated on the map. i 



i 



II. Little Orme's Head. i 



The Carboniferous Limestone forms Little Orme's Head, and 

 embraces an area of about 4 square miles, being double that of 

 Great Orme's Head. It forms two distinct ranges of hills, that on 

 the north extending from Eglwys Ehos to the sea, 2 miles by | mile, 

 including Little Orme's Head proper, the greatest elevation being 

 about 400 feet. The southern range extends 3 miles from Bod-y- 

 Sgallen to the sea, and includes Bryn Dinarth, a hill 400 feet high, 

 which is separated from the main mass of the range by a narrow 

 alluvial valley. These two ranges of hills afford very similar ex- 

 posures of the Lower Brown Limestone, more or less converted 

 into irregular beds of dolomite, with the Middle White Limestone 

 resting upon it, but without a trace of the Upper Grey Lime- 

 stone, all of which has been denuded away. The most important 

 geological feature is that the limestone of the northern range dips 



