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The Black Hill of Earlston. By J. G. Goodchild, 

 F.G.S., Royal Scottish Museum, Edinburgh. 



The foundation stones of the strata seen at the Black Hill of 

 Earlston are mostly ancient marine sediments which have 

 undergone many and important changes since they were first 

 laid down upon the sea floor. They were originally horizontal 

 sheets of mud, loam, silt, and fine gravel, and piled to a great 

 thickness one over the other. The few organic remains yet 

 found in them prove that they belong to the Silurian System of 

 the geological scale. These ancient sediments have subse- 

 quently been many times elevated into land, and afterwards 

 again lowered beneath the waters of the sea. The earliest of 

 the terrestrial movements to which these changes of level were 

 due took place at the close of the Silurian Period, and, as will 

 presently be shown, they must have come to a close before 

 Middle Devonian times. The elevations of the old marine 

 sediments into land were effected by the very slow movements 

 arising from terrestrial thrusts, which operated chiefly from the 

 North-west, South-eastwards. These thi-usts began by flexing 

 the old sediments into a series of gentle folds, and then, as time 

 went on, they compressed these folds closer and closer together, 

 until, eventually, the strata occurring over the whole area 

 affected, which must have been many thousands of square miles 

 in extent, became convoluted and puckered to such an extent 

 that a large part of them was turned upside down. Their suc- 

 cessional order, indeed, has thereby been so seriously disturbed 

 as to defy the efforts of the best Field-geologists who have 

 attempted to unravel their complexities, and to determine the 

 true thickness of the rocks of which they consist. 



