VICINITY of EDINBURGH. 413 
the clafs of rocks to which this appearance may generally be 
attributed *. 
Ir we imagine a vertical plane, to pafs from St Leonard’s 
Hill in an E.N.E. direction, which fhall cut Salifbury Craig, 
and continue through the right bank of the Hunters Bog, we 
fhall find the rocks difpofed in the following manner : 
St Leonard’s Hill. 
Sandftone. 
Porphyritic Greenftone. : 
Sandftone. : 
Salisbury Craig. 
Sanditone. 
Greenftone. 
Sandftone. 
Hunters’ Bog. 
Greenftone. 
Sandftone. 
Porphyritic Greenftone. 
Trap-Tuff. 
Bafalt. 
The 
* One of the greateft difficulties which geology as well as mineralogy has 
laboured under, is the multitude of fynonymous terms which have been applied 
to every individual foffil. Trap has fuffered from this difadvantage, perhaps 
more than any other variety of rocks; as above noticed, that name is derived 
from the fimilarity to the fteps of a ftair, which may generally be traced in the 
outline of a country, in which this rock abounds; and as it has been employed as 
a generic term by mineralogifts throughout Europe, I think it proper to use it, 
to the exclufion of whzn/eone, the name it bears in the writings of Dr Hurron ; 
a 
