SCIENCE-GOSSIP. 



199 



THE ROCKS OF THE ISLE OF MAN. 

 By Fred. J. Gray. 



*~pO the petrologist in general and the student in 

 -*• particular the Isle of Man afiords a very 

 good field for practical work. One may, with 

 great advantage, realise the ideas received from 

 different text-books on rocks, and institute compari- 

 sons between the illustrations contained therein 

 and the actual scenery and rocks found in rambles 

 through the island. No matter how descriptive 

 and minute in explanation be the text in such 

 books, or how excellent the diagrams or sketches, 

 they do not give anything like such a good idea, 

 or fix themselves so firmly in the memory, as one 

 look or practical examination of the rocks as they 

 stand where Nature placed them. 



Three of the great geological series are repre- 

 sented in the Isle of Man, viz. ; Lower Silurian, 

 Carboniferous and Pleistocene, in addition to which 

 there are rocks which may represent the Devonian 

 and Permian series. From a palaeontological 

 standpoint the place is equally good, the Carboni- 

 ferous and Pleistocene yielding many fossils, 

 amongst them being found examples of Pisces, 

 Cephalopoda, Gasteropoda, Coelenterata, Echino- 

 dermata, Crustacea, Annelida and Cirripeda ; 

 flints and fossil mammal remains having also 

 been discovered. The petrological specimens 

 include varieties of granite, greisen, pegmatite, 

 aplite, diorite, basalt, volcanic-ash and agglo- 

 merate, felsite, greenstone, clay, slate and 

 ironstone. The shores near the different towns 

 abound with pebbles of various rocks and 

 minerals. So that, on the whole, one is fortunate 

 who is able to spend a time devoted to the study 

 of petrology, through the rocks of this island. 



To see examples of these rocks, however, one 

 has to leave the beaten tracks, and a large amount 

 of walking is in many cases necessary. This is 

 nothing to the enthusiastic student, even tl 

 weighed down with bag of specimens, hammer, 

 etc. It is well worth the trouble, for the natural 

 result is that one sees the grand and rugged 

 scenery, whilst we find body and mind alike 

 strengthened, and secure material for future study 



The influence of geology on scenery is of course 

 always very great, but at the Isle of Man this is 



exceedingly well exemplified. 

 the mountains are round' ably by ice 



The shore scenery 

 uglas. Lax' in, and elsewhere, the 



cliffs, which arc of the Silurian rock, arc high, 

 grand and t Ml and La 



vc have contorted clay schi 



Mane and conglomerate, with 1 sheet 



known a* Scarlet Point . the long, low 1 



Langness Point and peninsula being a notable 

 example of the clay schist. To the north of the 

 island the Pleistocene succession is found, and here 

 we have a low shore of boulder clay and drift, 

 and at the point of Ayr a flat area of sand. 



The southern three-fourths of the island being 

 composed of the Lower Silurian rock elevated into 

 mountains, there are many valleys and glens, some 

 of extreme beauty, and the mountain streams con- 

 tain numerous waterfalls and cascades, for which 

 the island is justly renowned. Having introduced 

 the subject, I will pass on to a more detailed account 

 of it from a purely petrological point of view. 



The principal rock of the island belongs, gene- 

 rally speaking, to the Lower Silurian series, being 

 usually correlated with the Skiddaw slates. This 

 rock is found to make up practically the southern 

 three-fourths of the isle, being found at the Calf of 

 Man and Langness Point, and extending as far 

 north as Ramsey. It is also found at Douglas and 

 Laxey on the east, and at Port Erin and Peel on 

 the west. The rock is not, however, exactly the 

 same at all these places. It varies in colour, tex- 

 ture, bedding and other characteristics. Douglas 

 Head is a mass of dark-coloured, hard, contorted 

 shale, or clay schist, the beds being arranged at 

 all angles, and much faulted. At Laxey, the beds 

 are all conformable, fairly hard, of a light-grey 

 colour, and generally more slaty in appearance. 

 At Langness there is a great difference. There we 

 have contorted clay schist again, but of a brilliant 

 claret colour in some parts, and a light bluish- 

 green in others, all soft and shaly, and very easily 

 broken, hardly requiring the use of the hammer. 



The second series in point of area represented 

 in the island is the Pleistocene, which covers the 

 entire northern portion. A certain amount is also 

 found near Laxey and Castletown, and a band 

 of this formation extends across the isle from 

 Douglas to Peel, where it forms a valley between 

 the high ground and mountains of slate already 

 referred to. Along that valley the railway and 

 road to Peel both pass. 



A further stratigraphical series of which beds 



are found is the Carboniferous, this being repre 



by the Mountain Limestone, which occurs 



1 laces, viz., Castletown and Ballasalla, 



and a very small patch found at Port St. Mary 



limestone 1 exceedingly plentiful in fossils 



n great number having been chronicled. To 



the west of Castletown and al the head of 



a b Bay is a small quari ol blaci marble 



• north ol 1 ■ • 1 1 lo there are found beds 



1 .' red 1 oloui . 



