L. A. Necker de Saussure Voyage en Ecnsse. 179 



We begin to distinguish easily the shining plates of hornblende; 

 and higher up we at length perceive the associated feldspar. 

 The same phenomena occur in an inverse direction, in the parts 

 of the rock, which are again covered with beds of sandstone. 



The conical hill, called Arthur's-seat, is a peculiar conglome- 

 rate, named by Werner iraptiiff, though it resembles in no re- 

 spect a tuff, properly so called. It consists of large blocks of 

 sandstone, of clay iron-stone, of grunstein, and of fragments 

 of basaltic prisms, confusedly piled up, and joined together by 

 a paste of the nature of wacke, which is traversed by a great 

 many veins of calcareous spar, and others of a mixture of lime- 

 stone and red jasper. It is not arranged in strata, but rises into 

 a rounded hill without regular divisions, above a succession of 

 beds of trap and sandstone, similar to those described above. 

 It does not conform to these rocks on which it rests. Above the 

 conglomerate, a conical point ascends, which forms the sum- 

 mit, called Arthur's-seat. This point is entirely composed of 

 very regular prisms, placed in a vertical position. The rock 

 of which these prisms are formed is a porphyry, with a base of 

 earthy basalt, of a dull-greyish black, difficultly scratched by 

 steel, and easily melted before the blow-pipe into a black ena- 

 mel. In this basalt are enclosed, in sufficient abundance to 

 make them appear constituent parts, olivine, (peridot, Haiiy) 

 in very transparent small grains, of a greenish yellow, as also 

 rectangular plates of augite, (pyroxene, Haiiy) of a fine black 

 colour, and a lively lustre ; with thin plates also rectangular, 

 of feldspar, which is easily recognised by its changing reflec- 

 tion of light. 



Of the picturesque geological phenomena which occur on the 

 coast between Berwick, and Siccar-point, (near Cape Keale) where 

 the Edinburgh coal formation terminates, Mr. Necker has given 

 a very interesting description. Here we see the sandstone in 

 strata of little inclination, resting on the nearly-vertical beds of 

 greywacke, which they partially cover. The direction of these 

 two orders of strata is indeed the same, but their inclination is 

 absolutely opposite. For while the beds of greywacke dip to- 

 wards the south-southwest, and rise up towards the north- 

 northeast, those of the sandstone dip towards the north-north- 

 east, and rise up towards the south-southwest. There can be no- 

 thing more striking than this junction, completely laid open by 

 the waters of the ocean. It is uncommon thus to see in imme- 

 diate contact two classes of rocks of so different a formation, 

 and one of which must have preceded the other by a long se- 

 ries of ages. The sandstone does not rest immediately on the 

 greywacke, but some strata of a pudding-stone, or coarse con- 

 glomerate, having the same direction, and the same inclination 

 as that of the sandstone, divide the two. The pudding-stone is 

 in fact nothing but this same sandstone filled with pebbles, 



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