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V. — On the Geology of Cockburnlam, and the adjoining District, in Berwickshire ; 

 with a Map and Sections. By William Stevenson, Dunse. 



The portion of Berwickshire, of which the object of this paper is to describe 

 the more remarkable geological featm-es, comprises, within a very limited space, 

 an assemblage of phenomena of the highest interest, in relation to the Avonderful 

 changes which this part of our island has undergone in the earlier periods of the 

 earth's history. Its situation is immediately to the north of Dunse, and its area 

 is about 16 square miles, within which are comprehended the junctions of the 

 greywacke rocks of the Lammermuirs, with the strata of the old red sandstone 

 formation, and of the latter with the lower members of the coal measures. The 

 chief eminences within the district are Cockburnlaw, which attains a height of 

 912 feet above the level of the sea ; Dunselaw, 630 feet ; the Knock, Borthwick, 

 and Castlemains Hills ; and the Staneshiel, a hill of the same formation as Cock- 

 burnlaw, from which it is separated by a ravine of 300 or 400 feet deep, in which 

 the Whiteadder flows. The general topographical features of the district will be 

 best understood by reference to the accompanying map. 



In treating of our subject, we propose to describe, 1st, The stratijied rooks, of the 

 district ; and, 2dly, The igneous rocks, and the cJianges of structure and position 

 which have been effected by their agency upon those of aqueous origin. 



I. Stratified Rocks. 



1. The Greywacke of the Lammermuirs. 



The strata of this important series of deposits (the most ancient of the district 

 under consideration) are finely exposed in many localities, consisting of arena- 

 ceous and argillaceous beds, of great, but as yet, unascertained thickness, the for- 

 mer constituting the greywacke proper, and the latter the greywacke slate. The 

 oxides of iron and manganese are widely diffused among these strata. Mag- 

 nesia enters pretty largely into their composition ; but there seems to be an al- 

 most entire absence of calcareous matter, there being no beds of even impure 

 limestone interstratified with the greywacke, and but a small quantity diffused 

 through its masses. Sulphate of baryta is also very generally met with, in the 

 form of veins of various sizes up to a foot or more in width, and occupying fissures 

 in the greywacke. Near Elmford, the cleavage fissures of the greywacke strata 

 are filled with this mineral. 



No decided traces of organic remains have hitherto been discovered in the grey- 

 wacke of this part of the Lammermuirs. On some slabs from a quarry near 

 Hoard weel, some curious relieved markings appear, which may prove to be of or- 



VOL. XVI. PART I. I 



