AND THE ADJOINING DISTRICT, BERWICKSHIRE. 39 



with the secondary strata along the flanks of the Lammermuirs, belong as exclu- 

 sively to the Augitic family. In considering these, we shall follow the natural 

 order, by describing, 1st, the Felspathic traps, and their effects upon the grey- 

 wacke strata ; and, 2dly, the Augitic, or more modern traps, and the effects 

 which they have produced upon the more ancient rocks, both stratified and un- 

 stratified. 



1. Felspathic Traps. 



Rocks of this class are very abundant among the Lammermuirs, generally 

 occurring in the form of dykes or veins of various sizes, intersecting the grey- 

 wacke ; or in large masses constituting entire hUls. They consist of two or three 

 varieties of granite and syenite, with an almost endless variety of felspars, clay- 

 stones, and felspar porphyries. The following are some of the principal rocks of 

 this kind which occur in the district. 



Gh-anite of Gockburnlaw and Staneshiel. — This rock shews a great variety of 

 aspects at different parts of these hills. Near the outskirts of the mass, where it is 

 in contact with the greywacke, its constituent crystals are very small, and its 

 cleavage structures rectangular, and according with the strikes and cleavages of 

 the adjoining strata. On proceeding into the interior of the mass, however, the 

 rectangular cleavages due to its refrigeration, in accordance with certain lines, are 

 superseded by the structures resulting from the crystalline tendencies of the 

 granite, which have of necessity had more time for their proper development, in 

 proportion as the distances from the cooling surfaces increased. The rock, in 

 consequence, becomes harder, and its crystals larger and better defined, whUe it 

 is divided by its structural planes into large, irregular, pyramidal blocks. Its 

 most common character is that of a regular granite, composed of distinct crystals 

 of white quartz, red felspar, and black mica ; being identical, both in regard to 

 geological age and lithological aspect, with a granite which is associated with 

 greywacke near Fassney Bridge ; and which, from being intruded among the 

 strata of the latter, in conformable beds, caused much discussion between the 

 Huttonians and Wernerians. In some places, as, for example, on the south side 

 of the Staneshiel, about half way up the hill, sulphate of baryta is added to the 

 usual ingredients of the granite ; and near the top of that hUl small quartz veins 

 occur, containing galena and copper pyrites, though in very minute quantity On 

 the left bank of the Whiteadder, about 60 yards below Cockburn mill-dam, a 

 mass of syenitic rocks of extreme hardness appears in contact with the gi'ey- 

 wacke, and projecting into the bed of the river. This is evidently a process from 

 the Staneshiel hill, the granite of which, as well as that of Gockburnlaw (which 

 is indeed a part of the same mass), in many places passes into syenite. In fact, 

 after an attentive consideration of the phenomena presented by the transition of 

 one rock into another, and especially the changes effected upon both aqueous and 

 igneous rocks, at and near their junctions, of which many highly instructive 



