yiClNITT of EDINBURGH. 415 



abruptly at each end by the greenftone; in another, that fub- 

 ftance links fuddenly as it were into a gap in the ftrata, and be- 

 ing loft in rubbifh, has fomewhat the appearance of a dike. 

 Beyond this a double horizontal wedge of greenftone, with the 

 ends turned downwards, appears among the ftrata 5 and a little 

 farther, towards the north, a roundifh mafs of the fame fubftance 

 alfo occurs ', this has very much the appearance of an included 

 fragment, but the decompofition of the fandftone has juft be- 

 gun to expofe its connection with the rock above. 



On the fandftone, Porphyritic Greenftone (No. 3.) refts. The 

 colour of this is reddifh-brown ; the texture is fine-grained ', 

 and it contains finall fpecks of flem-coloured calcareous fpar. 

 It is traverfed in various places by veins of Hematitic Iron-ore 

 (No. 4.) accompanied with fulphate of barytes. Thefe two 

 fpecimens have very much the character of fome varieties of 

 porphyry-Hate, and on breaking one mafs, I obferved a tenden- 

 cy to a flaty arrangement. In different places of this quar- 

 ry, the greenftone afmmes a variety of appearances (No. 5. 

 and 6.), fome of which might be attributed to decompofition. 

 I do not conceive, however, that any external caufe has ever 

 had much effect upon this rock, although in fome places it has 

 entirely loft its luftre, (No. 7.), and might be miftaken for 

 trap-tuff, were it not for the fhape of the cryftals. 



Above this, the rock graduates into a highly cryftal- 

 line Porphyritic ftone, (No. 8.) the pafte of which is of a 

 brownifh-grey colour, very clofe-grained, with an uneven 

 fplintery fracture, containing both cryftals of felfpar and horn- 

 blende. 



In this quarry there are feveral inftances of slikensides, 

 one of which is rather remarkable, it occurs in an inclined rent 

 in the fandftone : the traces of the flip, (No. 9.), are horizon- 

 tal, 



