76 GEOLOGY OF THE LOTHIANS. 



stone, and limestone ; it appears to constitute the lowest rock 

 of the island, and is in general traversed by a multiplicity 

 of veins of calcareous spar, which is sometimes fibrous. The 

 other minerals which are met with in the rocks of Inchkeith 

 are common jasper, and Lydian-stone, the latter of which 

 forms contemporaneous imbedded masses and layers in the 

 limestone. Glassy felspar occurs in the basalt, which also 

 contains minute masses of steatite. 



A little to the west of Inchkeith, Inchcolm rises. A consi- 

 derable portion of this island is composed of greenstone, ex- 

 hibiting either the earthy, syenitic, or common appearance, 

 and which, by the felspar being replaced by steatite, fre- 

 quently passes into an imperfect serpentine. On the south 

 side of the island, a variety of greenstone occurs contain- 

 ing numerous scales of pinchbeck-brown mica ; it is traversed 

 by a number of contemporaneous veins of greenstone, which 

 frequently passes into steatite ; this mineral occurs also in 

 minute strings without exhibiting any such transition, and 

 in them sometimes there may be observed threads of ami- 

 anthus. On the south of the island, where a junction 

 of the trap and the sandstone is exposed, the latter dips to 

 the north at 52° ; while the greenstone, as it approaches 

 the sandstone, passes into a compact yellowish-white clay- 

 stone, a vein of which occurs running parallel (Plate X., 

 Fig. 1.) with the strata. With the exception of a body 

 of sandstone, which is enveloped in the greenstone, the 

 western half of the island is entirely composed of trap, hav- 

 ing in some places a slightly columnar disposition. Farther 

 up the Firth, the islands of Cramond, Carcaig, Mickrey, 

 Mickrey Stone, and Inchgarvey occur : from being entirely 

 formed of trap, however, these exhibit nothing interest- 

 ing. The greenstone of Cramond Island and Mickrey is 

 syenitic, the felspar being white and of a light brick-red 

 colour. At the mouth of the Firth, a range of trap islands 



