﻿412 Senry II . Soivorth — Geology of the Isle of Man. 



surface. The latter rests immediately on the schist, and I have 

 a number of specimens broken off from the very point of contact, 

 where unmistakable schist is immediately in contact with unmistak- 

 able limestone, and nothing intervenes between them, the beds at 

 the same time resting apparently conformably one upon the other. 

 This may be seen at Cushnahavin, a few yards north of the estuary 

 of the Santon brook ; a few yards to the south, as I have said, the 

 purple schists may be also seen in immediate contact with the 

 limestone, showing that no Devonian beds intervened. 



Fourthly, as to the red colour of the beds. This is undoubted, but, 

 as I believe, it has nothing to do with the beds being Devonian. At 

 the mouth of the Santon brook may be seen a sight which Mr. 

 Gumming rightly considers as one of the most interesting which a 

 geologist can see anywhere. The twisted and contorted schists 

 gradually change colour, and from being of a blue, and grey colour, 

 become striped with red bands, which are occasionally a foot and 

 a foot and a half in width, and eventually the whole rock, without 

 changing its character, assumes a beautiful purple colour. The 

 brook passes right through these purple schists ; some ten or fifteen 

 yards to the south of the brook the schists lie directly against and in 

 contact with the great beds of Mountain Limestone. At the point 

 of contact, and some distance beyond, the limestone is coloured of a 

 russet colour by iron. There are no interposed beds of red con- 

 glomerate, but the schists and the limestone are both of them stained 

 red with iron for some distance from the point of junction. Further, 

 I was told by a neighbouring farmer that a shaft had been pierced 

 into the limestone at the point of contact in search of iron-ore, 

 which had been found there. 



Where the schists and the limestone are in contact at Port St. 

 Mary, a similar excavation for iron has been made, and the limestone 

 beds are stained of a russet colour. 



The same thing occurred in Castletown bay on the peninsula of 

 Langness, where the deep blue slate may be studied in its normal 

 condition, both at the extremity of the headland and at a recently 

 sunk shaft made in search of copper about 500 yards from the 

 extremity of the headland. The schist between the two points just 

 named gradually changes colour and becomes highly charged with 

 iron, while the beds of limestone which lie in the bay go through a 

 similar change of colour. This shows that where the schist and the 

 limestone came into close contact, there has been a discharge of iron 

 which has discoloured the rocks on either side. This discharge 

 probably proceeded from one of the numerous trap veins which have 

 dislocated the rocks in a very extraordinary manner, and whose 

 meandering lines are very clearly marked against the differently 

 coloured rocks close by. It is this discharge of iron at this critical 

 line of junction between the limestone and the schist which may 

 possibly have led to the idea of there having been a series of Devon- 

 ian beds between the schists and limestones in the south of the Isle of 

 Man, but I am confident that no such Devonian rocks exist in that 

 part of the island. I do not say a word about the red sandstones of 



