VICENITY of EDINBURGH. 425° 
I now come, as propofed, to that divifion of the fubje& which 
relates to indurations. By induration is meant, a greater degree 
of compactnefs, obfervable in particular parts of ftratified rocks, 
than is ufual throughout their mafs. One part of a bed may be 
harder than another, confequently more indurated. But the in- 
duration here alluded to, is that which is fuppofed to have been 
effected, by an alteration in the denfity of the ftone, in confe- 
_quence of the action of heat. 
Turse phenomena are of a very ftriking nature, and were 
firft brought into notice by Dr Hurron ;, in them, he found 
evidence, to him perfeétly conclufive, of the igneous formation 
of whin, and, with that ingenuity and perfeverance which cha- 
tacterife the whole of his works, he did not fail to generalife 
his obfervations, and to place the facts, firft noticed in this {pot, 
in fuch a light, as to render them effentially ufeful to his. 
theory. 
Tue anxiety which the difciples of the Wernerian fchool 
have always evinced, to undervalue the merit of this obferva- 
tion, is a fure mark of the eftimation in which they hold it; 
and it is, therefore, very properly confidered by the fupporters — 
of the oppofite doctrine, as one of their ftrongeft holds. In the 
following lift, are comprehended moft of the varieties, which 
this indurated fandftone prefents on Salifbury Craig. 
No. 49. is a junction fpecimen*, taken near the fouthern 
extremity, of the Craig; here the greenftone is of the deep red 
tinge noticed at No. 17. 
Vou. VI. P. Tk.» 3H No. 
t 
* By junéfion /pecimen is meant, a {pecimen which exhibits the greenftone and 
the fandftone conjoined. : 
