110 GEOLOGY OF THE LOTHIANS. 



angles to the plane of the bed. On these dykes there re- 

 poses an extensive series of sandstone, slate, and ironstone, 

 but there are no opportunities afforded for examining the 

 connexions of the strata with the hanging side of the up- 

 permost vein. (Plate XIII. Fig. 1.) The other opening 

 where the Winchburgh trap rock is seen in contact with the 

 sandstone, is in a field on the side of the road at Muiryhall 

 (Plate XIII., Fig- 2.) ; it is highly satisfactory, and the 

 quarrying operations have exposed the several relations of 

 the rock in a manner sufficiently distinct. A mass of green- 

 stone rises through the sandstone, and, on arriving at the 

 surface, flows over it, forming an overlying body of variable 

 thickness, and issuing from this mass, a minute vein runs 

 a short course between the strata of sandstone, and de- 

 creases in thickness as the distance from the vein in which 

 it originates increases. The characters which the several 

 stratified rocks assume when next the unstratified, are here 

 well displayed, but are precisely similar to those which 

 may be remarked in almost every locality in the Lothians, 

 where the two classes of rocks are found in contact or 

 near connexion. The sandstone, as it approaches the green- 

 stone, gradually assumes a compact structure, till at last 

 it acquires such a degree of induration as to present the 

 appearance of a granular quartz ; while the greenstone, 

 as it approaches the sandstone, becomes felspathose. By 

 following the Ecclesmachen burn from Niddry Castle, stra- 

 ta of sandstone are seen cropping out in several places, ap- 

 pearing to constitute the bottom of the valley, while the 

 sides are composed of greenstones which rise into the emi- 

 nences of Tar Hill, Craig, &c. At the village of Eccles- 

 machen, several inconsiderable strata of limestone are to be 

 noticed in the bed of the stream, but though trap is in their 

 immediate neighbourhood, there are no junctions exposed. 



