And the adjoining district, Berwickshire. 43 



disturbed by their agency. Besides the veins and masses which are exposed, 

 there are, undoubtedly, many veins and extravasated portions concealed among 

 the strata. The principal masses of these traps which occur in the district are 

 the following : — 



The Cumledge trap-dyke is a large body of trap of irregular thickness, which 

 is seen in the bed of Oxendean Bm-n, near Cumledge House, and about 200 yards 

 from the Whiteadder. It is here a sort of amygdaloidal greenstone, abounding 

 in veins of zeolite, steatite, and other minerals, and is probably not more than ten 

 yards in thickness. On the west side it appears in contact with beds of a sort of 

 cornstone, which are excessively hard and crystalline at the junction, while the 

 trap becomes soft and earthy. On the east side a similar description of rock 

 occurs. From this spot to the Whiteadder the strata are Jiid by debris, but ap- 

 pear to belong to the coal measures, of which a fine section is presented a short 

 way below the place where the burn joins the Whiteadder, in a cliff of more than 

 eighty feet high. The shales, sandstones, and clays, are here seen dipping away 

 from the dyke at angles, which increase in proportion to the proximity of the line 

 of disturbance, until they become vertical, and even partially reversed. From 

 this place to Preston Bridge, the strike of the strata is very regular, and parallel 

 to the course of the dyke, which runs in a SSE. du-ection. At Preston Bridge its 

 thickness is upwards of 100 yards. The strata of the coal-formation come close 

 up to it on the east side ; while on the west it cuts off the old red standstone. 

 On the north bank of the river, about 300 yards above the bridge, it is seen in 

 contact with strata of whitish sandstone and grey calcareous shales, which seem 

 to be equivalents of those strata which elsewhere constitute the transition beds 

 between the old red sandstone and coal measures. From this place it may be 

 traced in the bed of the river, presenting, in general, the aspect of an amygdaloid, 

 until we reach a place called " Anglemyheart," where it passes into a beautiful 

 columnar basalt. The columns are irregular hexaedral prisms, not arranged ver- 

 tically, but dipping at high angles to west. The basalt is more crystalline, and 

 the columns more regular towards the interior of the mass. Towards the out- 

 skirts it passes into an olive-coloured greenstone ; and the latter graduates into a 

 trap-tuff, composed of fragments of greenstone and metamorphic greywacke, 

 agglomerated into a mass. 



This trap-dyke appears to run under the granite of the Staneshiel and Cock- 

 burnlaw, — not, however, directly under the centre of the granitic mass of these hills, 

 but more to the west side. In the glen or ravine between these two hiUs, and ex- 

 actly in the line of continuation of the Cumledge dyke, a mass of basalt occm-G, 

 which has burst through the older rocks. There is every reason to beheve that 

 an eruption has taken place from a crater at this locahty, and that the basalt now 

 occupies what was formerly a volcanic vent. A considerable quantity of trap- 

 tuff is seen in the bed of the river, in the vicinity of the basalt, and at intervals 



