12 ME. G. W. LAMPLUGH ON SOME EFFECTS OF [Feb. I9OO, 



in an advanced stage of preparation, my present object is briefly 

 to call attention to such structures as appear to be of more than 

 local interest, leaving the full statement of the local evidence for 

 the forthcoming Survey memoir. 



The general characters of the exposure are already well known 

 to British geologists. They were described early in the present 

 century by Berger, 1 Macculloch, 2 and Henslow, 3 and in greater 

 detail in more recent years by Gumming, 4 Home/ Clifton Ward, 6 

 Bernard Hobson, 7 and Sir Archibald Geikie. 8 The coast-line was 

 mapped on the 25-inch scale in 1892 by Mr. A. Strahan and myself, 

 and it was at that time that those anomalous features were observed, 

 which rendered necessary my later search for further evidence. 



II. Position and Extent of the Volcanic Outceop. 



The volcanic recks lie at the southern margin of a little tract of 

 Carboniferous Limestone 7 or 8 square miles in extent, and occupy 

 a broad craggy foreshore for a distance of about 1J miles, from 

 Scarlet Point on the south-east to Poolvash(Poyll Yaaish) Inlet on 

 the north-west, but nowhere reach for more than 200 or 300 yards 

 inland. The eastern portion of this belt consists of a chaotic mass 

 of coarse and fine fragmental volcanic material, traversed by ridges 

 of basaltic rock (the w augite-porphyrite ' of Hobson) which are 

 dyke-like in their mode of occurrence, but usually possess the 

 vesicular flow-structure and other characters of lavas. Entangled 

 among these rocks are many isolated patches of dark limestone, 

 ranging in size from blocks 1 or 2 feet in diameter to strips several 

 yards long and several feet thick, in which the original flaggy 

 bedding is still preserved. In the western part of the outcrop, 

 the volcanic material is made up almost entirely of tuff, often fine 

 in texture and calcareous in composition, in places exhibiting 

 excellent bedding and containing a few marine fossils. Here, 

 also, crumpled strips and dome-shaped lenticles of limestone are 

 sporadically distributed, increasing in size and frequency towards 

 the western junction of the tuff with the limestone. 



1 ' Mineralogical Account of the Isle of Man ' Trans. Geol. Soc. vol. ii 

 (1814) p. 45. 



2 ' A Description of the Western Islands of Scotland, including the Isle of 

 Man ' vol. ii (1819) pp. 570-71. 



3 ' Supplementary Observations to Dr. Berger' s Account of the Isle of Man ' 

 Trans. Geol. Soc. vol. v (1821) pp. 495-9(1 



4 ' On the Geology of the Isle of Man ' Quart. Journ. Geol. Soc. vol. ii 

 (1846) pp. 322-23 ; see also his ' Isle of Man ; its History, etc' London, 1848, 

 pp. 129 et seqq. 



5 ' A Sketch of the Geology of the Isle of Man ' Trans. Edinb. Geol. Soc. 

 vol. ii (1874) pp. 335 et seqq. 



6 ' Notes on the Geology of the Isle of Man ' Geol. Mag. 1880, p. 5. 



7 ' On the Igneous Rocks of the South of the Isle of Man ' Quart. Journ. 

 Geol. Soc. vol. xlvii (1891) p. 432 ; reprinted with some additions and 

 corrections in ' Yn Lioar Manninagh ' vol. i, pt. x (1892) p. 337. 



8 ' Ancient Volcanoes of Great Britain ' vol. ii (1897) pp. 22-32. 



