DR THOMSON ON TUB STRATA OF BERWICKSHIRE. 8? 



to the westward, in the direction of Coldatream, the schistose and cal- 

 careous sandstones, which frequently accompany the Berwickshire sand- 

 stone, make their appearance, and continue, with little change, to the 

 point at liirpham where I have already described them as lying over 

 magnesian limestone. The difficulty is to determine how these strata 

 are situated in relation to each other. It is evident that they are closely 

 connected : but we ask, is the position of the sandstone above, below, or 

 collateral with the carboniferous rocks ? I have stated the reasons which in- 

 duced me to class it with the new red sandstone. No argument can suffi- 

 ciently controvert my statements, except observations on the rocks in situ 

 demonstrating the contrary. Such I hold to be the experimenium emeu. 



The western boundary of the North Durham coal-beds is indicated 

 by the course of the river Till. For a little to the west of Duddo they 

 may be seen cropping out, and dipping from south-west to north-east I 

 have examined the strata in this neighbourhood, and am happy to be 

 able to add to the interest of this coal tract, by presenting a section of 

 the new shaft at Greenlaw- wells, which was commenced in 1832. For 

 this I am indebted to the attention of the son of the late intelligent over- 

 seer, in company with both of whom, and one of the proprietors (Mr 

 Young) I descended on the 8th of November 1833. Although the ob- 

 servations which follow are few, and perhaps of little moment in so far 

 as theory is concerned, still I think they are sufficiently important to re- 

 quire a place in the Transactions of our Club, because they are facts, 

 and facts are eternal. The shaft is about 31 fathoms in depth ; the sec- 

 tion presented by it, being that of varieties of sandstone and shale, oi 

 various extent and thickness. Over the coal which is worked, situated 

 at the depth of 27 fathoms, lies a black limestone, which is also observe I 

 underneath it. Above the limestone which is situated over the ccal, 

 f UT(! is a stratum of shale, or tills, as the workmen denominate it, filled 

 with impressions of palm-like plants and bivalve shells. In some places 

 the superjacent limestone is absent, and the shale occupies its place ; and 

 as it forms the roof of the level or drift, as it is termed, the fossil vege- 

 tables can be seen to great advantage. . . 



The whole series dips at an angle of 45, in a north- easterly direction 

 Hence it is obvious that the coal would soon disappear, and attain such 

 a depth as to render its being worked a matter of impossibility. Yet 

 coal is raised in four or five places, in a line from Duddo to the sea 

 The Cooper-eye coal, which is worked at Greenlaw-wells, is understood 

 to prevail in each of these localities, and therefore it must be raised or 

 brought nearer the surface in many points. This is rendered more pro- 

 bable, when we consider that there is an extensive trap-dike running 

 from the Till to the sea, which may have been the instrument in pro- 

 ducing the extraordinary convulsion in this carboniferous series in the 

 neighbourhood of the Tweed. 



It is to the rough-quartzosc sandstone that is observed at the *urfac 



