88 GEOLOGY OF THE LOTHIANS. 



mineral characters which these rocks exhibit are on a ge- 

 neral view similar to those which occur in the former 

 county ; there are, however, some which merit a detailed 

 description. The porphyry of the Garleton Hills has in 

 general a basis of a largely foliated clinkstone, inclosing 

 crystals of felspar ; it passes into clinkstone, and in other 

 parts into compact felspar; and associated with these porphy- 

 ry and clinkstone rocks, there occurs at the Abbey toll of 

 Haddington a felspar tufa, containing imbedded angular 

 fragments of porphyry and compact felspar. Much of the 

 country in the neighbourhood of Linton is composed of a 

 highly felspathic greenstone, which passes in many places 

 into claystone. The augite and felspar which form this 

 rock are, from being highly impregnated with iron, of a 

 brownish- red colour ; it is very small granular, exhibiting 

 in some places a tendency to a tabular arrangement ; and in 

 the quarry of Pencraik, where the felspathic greenstone is 

 worked to a considerable extent for road material, it is tra- 

 versed by numerous veins of sulphate of barytes, associated 

 with calcareous spar and fibrous brown haematite. 



In describing the relations of this great deposit of trap 

 and felspar rock, to the stratified formations, we shall com- 

 mence at the southern extremity, which rises above the vil- 

 lage of Garvald, forming Whitelaw Hill. At this point the 

 strata of red sandstone are found dipping at 10° to S.W. 

 by S., thus abutting against the igneous rocks, — a position, 

 however, which they are far from universally holding ; for, 

 in tracing the sandstone round the unstratified rocks, it is 

 found in many places to sink under them, or to be inclined 

 at a small angle. Such apparently unchanged positions of 

 the strata may, however, easily be reconciled with the in- 

 trusive origin of trap or felspathic rocks ; if it be remem- 

 bered that much of this ignigenous mass may be in an over- 

 lying position, and occurring only as a great body, which, 



