211 



THE GEOLOGIST. 



is of a dark ochreous colour, in fact, just the colour of the highly de- 

 composed Silurian pebble, and seems perfectly to answer to its final 

 debris. The stones in good preservation, are much striated, and the 

 boulders beautifully smoothed and grooved. In this arena, encircled 

 partly by rock (Silurian) with boulder clay in section, and partly by 

 the refuse heaps, the student of glacial phenomena may find ample oc- 

 cupation. Ice-scratched boulders of limestone and intercalated iron- 

 ore, are there thrown to light ; while lying out exposed, are huge blocks 

 of the former, marvellously cut and hacked in every possible direction. 

 The effect of turbid water upon stone is shown here. The limestone 

 blocks within its influence have undergone great decomposition, and 

 are moulded down into grotesque figures and shapes, similar to what 

 are seen on the surface of limestone commons, and used for orna- 

 mental rock-work. Their surfaces are rough as sandstone, coated 

 with a fine, almost impalpable, red powder. They are imbedded in 

 a dark brown substance, probably " Black Mack," described by Mr. 

 Cameron, vol. xix. page 27 of the ' Quarterly Journal of the Geolo- 

 gical Society.' 



When the stratified beds in the boulder clay rest upon the rock, 

 although the rounded or planed outline may be preserved, it is found 

 to possess a much rougher surface than when covered, by the unstra- 

 tified boulder clay. This is seen on the rounded rock by the via- 

 duct before noticed ; one side of which is covered by the following 



beds : — 



Soil. ft. in. 



Boulder clay, with, striated stones 3 0 



Large stones and sand ...20 



Pebhles mixed with sand 16 



Grey sand 6 



Larger pebhles 3 



Sharp grey gravel 3 



The Silurian rock under these is beautifully hollowed ^nt and 

 rounded, but it is extremely rough to the hand, is very soft, and 

 shows symptoms of decay. 



In a limestone quarry, north-west of Ulverstone, in a well-sinking 

 nearer the town, and also, I believe, in the railway-cutting, rough- 

 ened and curiously-shaped limestones, similar to those near the iron 

 ore, have been met with, lying under stratified gravels, capped with 

 boulder clay. In the quarry instance, I imagine the upper bed has 

 been much broken up, antecedently to the moulding and roughening 

 of the fragments. They are imbedded in a soft plastic clay ; clearly, 

 I think, a deposit from water. 



But there is another, and perhaps more difficult problem connected 

 with the boulder clay, which is, when loose gravels and sand, in no 

 respect differing from that deposit in lithological character, lie next 

 the surface-soil. 



This is the case on Gill Brow: a moraine bank, a mile to the 

 south-east of Lindale moor, at about 300 ieet elevation above the 

 sea. 



