GUMMING ON THE ISLE OF MAN. 319 



the south-eastern side of the island, and thence round by Jurby and 

 Point-of- Ayre to Ramsey, there extends a wide expanse of fifty square 

 miles of Pleistocene deposits, presenting cliffs both in the eastern 

 and western sides of the island, whose height is from 50 to 200 feet, 

 and which are subject to very rapid encroachments from the rake 

 of the tide, which sweeps up and down the channel. 



The northern shore, in the neighbourhood of Kirk-Bride, is low 

 and flat, and is very rapidly extending. 



A ridge of sand hills occupies a line running from Blue Head 

 to about four miles north of Ramsey, between which and the 

 mountain-chain lies the swampy plain of the Curragh, once occu- 

 pied by a number of small lakes, which have been gradually filled, 

 up or drained, but which were laid down in Chaloner's Map of 

 the Isle of Man, published in 1656. The mountain-chain of the 

 schists along its northern boundary sinks as precipitately into ihh 

 Curragh as it does into the sea at the south-western extremity of 

 the island. With respect to the general arrangement of these schists, 

 they dip off S.E. by S. and N.W. by N. from the before-mentioned 

 ridge. A close examination shows that they mantle round a series 

 of nuclei forming a rather irregular curved line from the Calf to 

 Maughold Head*. 



There is good reason for believing that these nuclei may be 

 granitic bosses ; and in two cases there is no doubt of it, the granite 

 itself appearing at the surface in a characteristic dome-shape. The 

 first of these occurs in the neighbourhood of Laxey, near the head 

 of the Dhoon river ; and the second is on a grander scale on the 

 south-eastern side of South Barrule, where it has also protruded 

 itself into the schist, having been reached in the workings of the Fox- 

 dale minef. Of the probable age of these granitic domes I shall 

 have hereafter to speak, and at present I would only mention that 

 they do not appear to have been older at any rate than the car- 

 boniferous limestone. The boulders of the Barrule granitic boss 

 occur in the tertiary formations of the south of the island, but I 

 have not as yet seen any indications of them in the Old red con- 

 glomerate. 



Along the mountain-chain in various places we meet with gneiss 

 and other metaraorphic rock, greenstone, and massive quartz-rock, 

 with abundance of mica. And generally reposing upon these, 

 though occasionally interstratified, we have the series of clay schists 

 with interposed beds of grauwacke, which constitute the body of 

 the island. 



These schists are highly ferruginous, and in lithological character 

 somewhat softer than the generality of the rocks of the Snowdonian 

 range : I have anxiously sought for fossils to determine their age, 



* Slicudhoo, Sartcl, Rock Mount and Contrary Head may perhaps he regarded 

 as prominent points of a secondary ridge on the north-western si(U;, in which i)or- 

 phyritic greenstone is developed at Rock Mount and Cronck-y-Voddy. 



t See Section across the island, PI. XIV. It is worthy of notice that hoth in 

 this case and at Laxey the intrusion of granite has improved the i)roducc of tlic 

 mine. 



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