﻿JSenry S. Soworth — Geology of the Isle of Man. 457 



as my friend Mr. Binney calls it ; and lastly, we have beds evidently 

 contemporaneous with, and made under precisely the same conditions 

 as the Boulder-clay proper, composed of a kind of soft pudding-stone, 

 of boulders imbedded in a matrix not of clay, but of disintegrated 

 limestone. 



The proportion of lime from the clay in various parts of the 

 island is given by Mr. Gumming in Appendix I. of his work, and 

 fully confirms this argument, and, as that author says, " indicate 

 the extremely local character of the contents of a great part of the 

 Boulder-clay." (Ibid. p. 306.) 



Let us now turn once more to the red conglomerate. Superfi- 

 cially it will be conceded by those who see it that it resembles an 

 indurated Boulder-clay formation of a red colour. This was, in fact, 

 remarked by Mr. Gumming, who says of it at one place, "It looks 

 extremely like a consolidated ancient Boulder-clay formation, only 

 there is more approach to regular bedding, more regularity of strati- 

 fication, as in the drift-gravel deposits." (op. cit. 8-9.) The word 

 " ancient " in this extract must be accepted as covering Mr. Gumming's 

 theory in regard to the deposit ; while as to the regularity of the 

 layers of boulders, this is, I take it, in a great measure imaginary. 

 I noticed no such peculiarity except in very local instances. The 

 red colour I have already explained as resulting from the formation 

 being made up of disintegrated local rocks of an ochreous colour. 

 Where the schists and limestones are not purple, the conglomerate 

 exists without its red colour, and I have specimens by me showing 

 the gradation from a perfectly grey pudding-stone of limestone to 

 one quite russet in colour. The inclosed blocks, as I said in my 

 former paper, consist for the most part of boulders of the adjoining 

 limestone, many with their edges hardly rubbed at all ; and the 

 whole deposit, but for its colour and tenacity, is very like the mass 

 of undoubted Boulder-clay forming Hango Hill, in the centre of the 

 Bay of Gastletown. 



The situation of the conglomerate is also that of a drift deposit. 

 It caps the hills and higher ground, as at the Brough and at Langness 

 Point, and at the latter place may be studied in close proximity 

 to similar deposits without the red colour, which have been de- 

 scribed by Mr. Gumming as Boulder-clay. In every sense I believe 

 therefore the red conglomerate to be a glacial deposit, and in no 

 sense a Devonian one ; and as such a striking example of the law 

 prevailing among the glacial deposits of the island in " changing in 

 composition and tallying in chemical character as well as in litho- 

 logical appearance and colour with that of the adjacent rock." 

 (Gumming, op. cit. p. 113.) 



I have not yet referred to what seems to me the most important 

 result of this rectification, and which indeed induced me to pro- 

 secute my inquiry. I have said that the conglomerate differs from 

 an ordinary Boulder-clay deposit in one important respect, namely, 

 in its compactness and solidity. This quality it shares with much 

 of the grey conglomerate with which I have compared it. The 

 cause of this density we must now inquire into. One horn of Gastle- 



