46 MR STEVENSON ON THE GEOLOGY OF COCKBURNLAW. 



the Castleknowes, the old red sandstone strata are seen dipping away from the 

 dyke, and divided by cleavages coiTcsponding to those of the trap Avhicli are 

 NNW. by ENE. Nearer the dyke they are much shattered, and are very hard and 

 crystalline. 



Tlie trap of Grindean, is a basaltic ridge which runs in a SSE. direction, and 

 appears to be connected with a line of fault similar to that of the Cumledge dyke, 

 which runs parallel to it, the old red sandstone strata appearing on the east side, 

 and those of the coal measures on the west j while the distance between the two 

 formations is much too small to admit of the strata, occupying an intermediate 

 space in the series, being brought on. The usual effects have Ijeen produced by 

 the trap upon the adjoining sandstones. In some specimens the transition from a 

 rubbly sandstone to a beautiful compact jasper is finely shewm. 



A very interesting cu-cumstance observable with regard to all the augitic 

 traps in this district, is, that their course is either in a NNW. direction, or in one 

 at right angles thereto, viz. from WSW. to ENE, — and these are invariably the 

 directions of their cleavages. They likewise appear to be all connected together, 

 forming one great system, indicative of one epoch of eruption. Thus the trap of 

 Borthwick hill is connected with that of Oxendean Commonhaugh, while the lat- 

 ter joins that of Dunselaw, by means of a ridge running by St Mary's Cottage. 

 The Castleknowes trap, again, joins the Cumledge trap-dyke to Dunselaw. An- 

 other large trap-dyke (a small portion of the course of which is laid down on the 

 accompanying map), can be ti-aced from Raecleughead hill by Langton, Gruel- 

 dj'lces, &c., for several miles in an ENE. direction, and seems to join the pro- 

 longation of the Cumledge dyke in the neighbourhood of Edrom, about four miles 

 from Dunse. A line drawn from the Castlemains hill in an ENE. direction, 

 passes through the basaltic rocks of Anglemyheart, and meets the trap of Grin- 

 dean. This line appears to be that of an extensive fault, the effects of which are 

 manifest in the extraordinary disturbance of the old red sandstone strata, at the 

 end of the Prestonhaugh section, near Anglemyheart. Between the latter place 

 and Grindean, this dislocation (which is probably associated with a trap-dyke) 

 appears to separate the old red sandstone and coal measures, the latter being 

 thrown down on the south side ; but, unfortunately, no section is exposed in the 

 course of this line. 



The consideration of the agencies which have influenced the directions of the 

 trap-dykes and Mnes of fault within the district, and changed the positions and 

 characters of the sedimentary rocks, is of great geological interest, but the princi- 

 ples involved are of too general a character to admit of being discussed in a me- 

 moir, descriptive merely of a small district. We therefore abstain from theorizing 

 upon the facts adduced, the more important inferences which these suggest being 

 for the most part sufficiently obvious. The views of the author on this branch of 

 the subject, are also in part indicated on the Map and Sections, lithographed on 

 Plate II. 



