477 



(1.) The Felspathic rocks comprehend all those igneous rocks 

 associated with the greywacke strata, consisting of the granites, 

 and syenites, and old porphyries of Cockburn-Law, the Stane- 

 shiel, the Knock Hill, Blackcrstone Hill, &c. The central parts 

 of these igneous masses present the most crystalline appearance, 

 consisting there of pyramidal and wedge-shaped blocks. In those 

 parts approaching to and in contact with the greywacke strata, 

 a rhomboidal parallelepiped structure prevails, — which also charac- 

 terises the aqueous rocks when in contact with the igneous. It is 

 interesting to notice the eiFect produced on the greywacke strata, by 

 the outburst through and among them of these igneous rocks. Where 

 the two kinds of rocks are immediately in contact, all signs of stra- 

 tification in the greywacke have been obliterated ; and, indeed, these 

 strata appear to have been metamorphosed into syenite. 



(2.) The Augitic trap-rocks exist almost entirely among the 

 more recent aqueous rocks, viz. the old red sandstones and coal- 

 measures. They are seldom or never seen within the range of the 

 greywacke formation, at least in this neighbourhood. 



These augitic traps exist both in the form of narrow dykes, and in 

 that of great masses constituting hills. Of the former, the Cum- 

 ledge trap-dyke is a good example. It is seen in the bed of Oxen- 

 dean Burn at Cumledge House, and there forms in amygdaloidal 

 greenstone, abounding in veins of zeolite, steatite, and other mine- 

 rals. The width of the dyke at this place is about ten yards. The 

 average direction of the dyke is NN.W. and SS.E. It has had the 

 effect, as usual, of hardening the strata on each side of it. This dyke 

 has been traced by the author for a considerable distance, running 

 through both the old red sandstone and coal-measure formations. 

 It appears also to reach into the granite of the Staneshiel and Cock- 

 burn-Law. 



An overflow of amygdaloidal trap is to be seen on the left bank 

 of the "\Miitadder, below Cockburn Mill, forming a bed of about four 

 feet thick, and lying above the old red sandstone strata. There are 

 large accumulations of greenstone at Borthwick and Castle Mains. 

 Dunse-Law is also composed of basalt. 



In the second part of his papei% the author shewed that the out- 

 burst of the granite and other felspathic rocks had taken place simul- 

 taneously with the upsetting of the greywacke formation, and before 

 the deposition of the old red sandstones. He also stated, that when, 

 after the deposition of the coal-measures, a new outburst of igneous 

 rocks took place, the Lammermuir chain probably received an ad- 



