126 GEOLOGY OF THE LOTHIANS. 



Near the point which constitutes the eastern boundary of 

 Inverkeithing bay, a tufa occurs which forms mural sea-cliffs 

 for a considerable way, and in some parts differs in character 

 from those tufas which are so frequently met with associated 

 with the trap rocks of the Lothians. It is composed very 

 generally of a yellowish-white claystone felspar, in which 

 variously shaped and sized masses of felspar, greenstone, 

 bituminous shale, and sandstone, are imbedded, and passes 

 into a tufa, of which the basis is an earthy greenstone, con- 

 taining greenstone fragments which are sometimes amygda- 

 loidal. Throughout the whole extent of this tufa there are 

 indications of a more or less perfectly bedded structure, the 

 separations into strata being produced by a change in the 

 size of the imbedded fragments. The connexion of the 

 sandstone with the tufa is in two places exposed : at one of 

 these, which is near St David's, it exhibits numerous marks 

 of derangement ; and a series of strata, consisting of alter- 

 nations of blackish and white slaty sandstone, which is 

 shifted in one place for several inches, is thrust up amongst 

 a completely compact white sandstone. 



The other point where the junction of the two rocks is 

 visible, is at the eastern extremity of the tufaceous mass ; 

 there, a vertical stratum of sandstone, several yardsin height, 

 by about three feet in breadth, is completely enveloped in it, 

 standing out from the strata of tufa which, on both sides of 

 it, have a westerly inclination. In regard to position and 

 structure, there are appearances in both which indicate, 

 that in the tufa there had been a cause adequate for dis- 

 placement, and also for producing a change in mineral struc- 

 ture; for masses of the sandstone are bent amongst the 

 tufa, and, as sandstones in contact with the more crystalline 

 trap aggregates, become intensely indurated, and make 

 the usual transition into quartz rock. 



From this junction of the sandstone with the tufa to 





