D. Mackintosh — Age of Floating Ice. 17 



the beacli close by, it is clear that, while this clay was in course of 

 being accumulated, an ice-laden current from the far north must have 

 mingled with the local currents of the Glacial sea.\ The brick clay, 

 or uppermost drift, is usually of a reddish colour. It contains very 

 few large boulders, but a considerable number of small rounded 

 stones, which consist of Lake District porphyry, Eskdale and Criffell 

 granite, Silurian light-coloured grit or sandstone, local limestone, 

 shale, etc., etc. The stones in the brick clay are generally more 

 flattened on one side, deeply and uniformly grooved, and more 

 polished than in the blue clay, so that if any member of the Colwyn 

 drifts is to be exclusively elevated to the rank of a Glacial clay, this 

 brick clay, and not the blue, ought to have the preference ; and yet 

 the submarine accumulation of this clay is, I believe, admitted by 

 all geologists.^ 



JBetioeen Conway and Bangor. — The Boulder-clay west of Conway 

 seems to be on the horizon of the lower brown member of the 

 northern drift. About Penmaenmawr, sand and gravel may here 

 and there be seen overlying this clay which, near the entrance of 

 the tunnel, attains a thickness of at least 60 feet. It clings to the 

 base of the steep slope of Penmaenmawr hill, is often a real pinel, 

 and contains northern erratics mixed with blocks which must have 

 fallen into it from above when the ice-laden sea beat furiously against 

 the flanks of the Snowdonian mountains. The Boulder-clay thins 

 out upwards under a talus of recent screes which thins out down- 

 wards. Between the west end of the tunnel and Llanfairfechan 

 there is an unusually crowded Boulder-scar, which contains stones 

 from the north, including both Eskdale and Criffell granite. At 

 some distance from the sea, above Llanfairfechan church, a brook 

 has revealed a good section of a knoll, consisting (at least partly) 

 of pinel which is a facsimile of what I once saw near Baycliff, 

 Morecambe Bay. One of the numerous included boulders reclined 

 on a thin bed of laminated loam, exactly in the same manner as I 

 had seen near Baycliff. A great thickness of gravel and sand, ap- 

 parently resting on Boulder-clay, is exposed in the cutting at the east 

 entrance of the tunnel through Bangor hill. At the entrance to the 

 next tunnel on the west side of Bangor valley, the Lower Boulder- 

 clay (of which only patches remain) has been dovetailed into sand 

 and gravel. Here and there on both sides of the valley, above the 

 level of the sand and gravel, this clay, often joartaking of the cha- 

 racter of pinel, may be seen filling up recesses. Traces of a blue 

 clay may likewise here and there be discovered. The obliquely 

 laminated and contorted sand and gravel near the Station (and which 

 is only a part of an extensive terraced deposit, running southwards 



1 I fear that Miss Eyton, who has made gome impoi'tant contributions to Post- 

 tertiary geology, has been misinformed about the existence of blue clay around Crewe. 

 I could see or hear nothing of it, though I found that some persons gave the name 

 blue clay to the upper red brick clay with greyish-tinged fractures, which there 

 oyerlies the middle sand and gravel. 



2 It is not, however, the only shell-bearing clay, for shells have been found in the 

 lower brown clay at Llandudno by Mr. Darbishire, and by others in the same clay 

 in Lancashire and Cheshire. 



VOL. IX. — NO. xci. 2 



