OF EAST LOTHIAN. 47 1 



claystone ; and this either into basalt or compact 

 felspar ; and these into porphyry-slate, which 

 forms in every case the summits of the obtuse, co- 

 nical, and isolated hills throughout the county. 

 A passage into greenstone was indicated, by inter- 

 posed particles of hornblende observable in the 

 rock, at the top of Traprain and North Berwick 

 Laws. 



It was also given as a new and corroboratory il- 

 lustration of the Neptunian theory, that in those 

 portions of the trap formation where particular 

 circumstances, existing at the moment of consoli- 

 dation, have given rise to a porphyritical struc- 

 ture of the whole series, similar shades of grada- 

 tion in the felspar crystals, from mechanic to che- 

 mical or crystalline texture, were to be perceived. 

 This very interesting fact, resulted from a minute 

 examination of the successive beds of trap, which 

 begin on the northern bank of the river, near the 

 town of Haddington, and terminate upon the 

 highest point of the Garltons, upon which the sig- 

 nal-post has been erected. Thus, in the bed, 

 which rests immediately upon the trap-tuff, at the 

 Abbey Quarry, and which is both porphyritical and 

 amygdaloidal, the felspar approaches very nearly 

 in its characters to the disintegrated subspecies ; 

 yet, at the same time, has distinctly the prisma- 

 tic form, indicating (if we be allowed to rea- 

 son from well-known chemical phenomena) a di- 



G 0? A. 



i 



