74 GEOLOGY OF THE LOTHIANS. 



Kirknewton and Lawhead, and appears to terminate at 

 the Linhouse water near Longhaugh Mill. The hills of 

 Auchinown, Morton, and Corston, form a part of this trap 

 range. From Longhaugh Mill to Linhouse, the bed and 

 both sides of the stream exhibit one of those alternating 

 groups of variously coloured shales and red sandstone, 

 which so often occur, both on the large and small scale, as- 

 sociated with the white sandstone series of the Lothians. 

 A short distance to the eastward of the stream the strata are 

 cut off by the trap-rock, which constitute all the hills on that 

 side. Opposite Linhouse it sends out a great dyke of grey 

 compact basalt, which crosses the river ; it cannot be traced 

 on the western side of the stream, but, judging from the 

 external aspect of the country, it is probable that it ter- 

 minates near this point. To the south of this trap-dyke, 

 nothing in any way interesting presents itself; but in the 

 course of the Linhouse water, there are numerous expo- 

 sures of the white sandstone and its concomitant shale 

 strata ; which form, without any visible association with 

 Plutonic rocks, a wide extent of moor ground, bounded on 

 the south by the red sandstone hills which constitute the 

 western extremity of the Pentland range. The greenstone 

 of Dalmahoy rests upon white sandstone dipping west ; but 

 as it is covered at the planes of contact, its aspect, if there 

 changed, cannot be seen. At the western extremity of this 

 trap range, at Longhaugh Mill, there is a very satisfactory 

 -junction of the greenstone and sandstone, both of which 

 are much altered in mineralogical character ; the strata 

 of sandstone become vertical or exhibit various undula- 

 tions, and are indurated into a granular quartz, while the 

 greenstone with which they are in contact passes into a very 

 compact greenstone or a felspar. At the southern extre- 

 mity of Auchinown Hill, and at the farm of Harper Rig, 

 a dyke of greenstone crosses the stream, running parallel 



