in the Neighbourhood of Edinburgh. 45 



granted that any such elevation as that here supposed has taken 

 place, there seems to be every reason for ascribing this cause to 

 that epoch. 



Several years have now elapsed since this interesting section 

 was first laid open, and the public are indebted for the preserva- 

 tion of so instructive a record of the changes and revolutions 

 which have given rise to the present state of the earth, to the 

 consent of the Magistrates of the City then in office, obtained 

 through the active exertions of the distinguished Professor of 

 Natural History in this University, and of his excellent friend 

 the late much lamented Treasurer of this Society, Mr Thomas 

 Allan of Lauriston, whose whole life was spent in the cultiva- 

 tion of science and in contributing to its advancement. 



Postscript. — Since the foregoing pages were written, Mr 

 Macgillivray, of the Royal College of Surgeons, has very oblig- 

 ingly put into the hands of the author, a sketch of the section of 

 the Castle Hill, made by him when it was first laid open in 1829, 

 from which it appears that a mass of trap was then exposed to 

 view, lying beneath the disturbed strata. This igneous rock was 

 so soon covered up in making the road, that it escaped general 

 notice. It is described, however, by Mr Macgillivray as being 

 totally different, both in appearance and character, from that up- 

 on which the Castle is situated, and more nearly resembling the 

 dyke that was met with in excavating for the foundation of the 

 Cowgate Bridge. 2 



