STOCKBRIDGE-BELL'S MILLS. G3 



claystone. The sandstone, when in connection with the 

 greenstone, is much indurated, and contains grains of iron- 

 pyrites distributed through it. (Plate VII. Fig. 3.) In 

 Broughton Street, which runs across the northern acclivi- 

 ty upon which the city of Edinburgh is built, trap again 

 occurs associated with sandstone. 



As the greenstone has been well exposed by quarrying 

 operations, its various modes of connexion with the strata 

 have been disclosed, and the result of all these observations 

 is, that it has been protruded through the strata in some 

 places parallel to their direction, and in others has crossed 

 them at various angles. From the upper surface of this 

 dyke of greenstone another takes its origin, running through 

 the sandstone to the distance of three feet and a half ; at its 

 point of contact with the principal mass, its breadth is 

 about one foot, and thins out gradually as it recedes from it. 

 The sandstone on approaching the greenstone becomes indu- 

 rated, while the greenstone acquires a compact structure, and 

 is traversed in several places by veins of amethyst, common 

 quartz, and calcareous spar. Besides these veins others 

 have been observed in the neighbourhood of Edinburgh, 

 but all are now completely covered. In Lothian Street 

 one of these veins occurs associated with the strata, dipping 

 to the east ; and at the Custom-House in Albany Street and 

 Leith Walk, there were at one time interesting exposures 

 of trap-rocks and of the phenomena attending their relations 

 to the various sandstones and shales.* 



In the bed of the Water of Leith three other trap-dykes 

 occur, the first of these veins, on proceeding up the stream, 

 is to be observed a short way above Stockbridge ; one of its 



* In the first volume of the Edinburgh Philosophical Journal these trap- 

 rocks are all minutely described by Professor Jameson. 



