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Carboniferous limestone, two remarkable things are found 

 associated. ist — As the clay comes nearer to the bed on 

 which it rests it becomes more and more dense and tough, 

 resembling in some places a solid rock, and quite as difficult 

 to cut through, and the colour changes from the usual reddish 

 tint to a dark grey or bluish black, corresponding in a measure 

 with that of the present rock. 2nd — The surface of the rock 

 is found to be cut off to a general plane, covered with flutings 

 or shallow grooves frequently highly polished, and scratchings 

 on these grooves, not parallel but forming slight angles with 

 each other, but all in the general direction of the grooves. 

 The upper surface of boulder clay hills varies very much in 

 some parts of the district, sometimes forming a series of un- 

 dulations, which are quite unconformable with the rock below, 

 and frequently taking the shape of detached rounded masses. 

 In the first case the hollows are often filled with beds of sand, 

 gravel, and finely laminated clay; and very often in sections 

 of these rounded hills, when exposed in railway or other 

 cuttings, their beds of fine sand and gravel are found at a short 

 distance from the subsoil, and having the same curvature as 

 the surface, and in these beds minute and greatly worn frag- 

 ments of wood have been observed interstratified. In exca- 

 vations made during the building of the County Antrim Jail, 

 some very remarkable sections were obtained ; in one where, 

 at a depth of about ten feet through this clay, the Keuper marl 

 beds were reached, it was observed that large lumps of fine 

 sand were dispersed in a confused way through the clay, and 

 mixed up with these were many roots and portions of trees. 

 In another section, a short distance from this, a bed of finely 

 stratified sand interposed between the marls, and a thin vein 

 of clay, without boulders, supporting other strata of sand. It 

 was pointed out that the characteristic phenomena of this 

 formation were unique, being different from any of the previous 

 deposits in earlier epochs of the world's history, and that 

 some new cause, or set of causes, not hitherto at work, must 



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