92 GEOLOGY OF THE LOTHIANS. 



portions may consist of amygdaloid, or be rendered porphy- 

 ritic by containing numerous crystals of felspar. Veins of cal- 

 careous spar, associated with quartz, traverse the greenstone, 

 and both these minerals occur crystallized in drusy cavities. 

 Nearly opposite the Lamb island a few minute strata of fetid 

 limestone appear, but nothing in regard to their relations with 

 other rocks can be ascertained. At North Berwick a mass 

 of trap runs boldly into the sea, intruding more or less pa- 

 rallelly among the red sandstone strata, forming one side of 

 the harbour. The island of Craig Leithie lies immediately 

 opposite the trap of the harbour of North Berwick, indicat- 

 ing, as do all the other trap islands which skirt this coast, 

 a continuity with the trap-rocks occurring on the shore. 

 About a mile from North Berwick the hill of North Ber- 

 wick-Law rises, with its beautifully conical form, above a 

 comparatively level country ; in its geological structure, 

 however, it exhibits nothing interesting, and its relations 

 to any of the stratified rocks are in no place observable. A 

 brownish-red felspathic greenstone, associated with trap- 

 tufa, forms the lower part of the hill, while the summit is 

 composed of a clinkstone, which exhibits a slightly tabular 

 arrangement ; its mode of connexion, however, with the 

 greenstone and the tufa is completely obscured. The series 

 of strata which sinks under the trap of North Berwick Har- 

 bour, is, after being visible for a short space, covered up 

 by a sandy beach, through which rocks of green trap-tufa 

 are afterwards found emerging. This tufa is in many 

 places distinctly stratified, and is composed of variously 

 sized fragments of red sandstone, limestone, and trap, ce- 

 mented together by a basis of comminuted trap. Veins of 

 greenstone, in one or two places, traverse the tufa, and some, 

 by effecting changes on it, produce those appearances, which 



