420 : ‘On the ROCKS in the 
brown colour. On breaking into the rock, it exhibited 
(No. 31.) * the concentric lines fo common in decompofing 
greenftone; and beyond this, the ftone prefented a degree 
of frefhnefs, with a very coarfe grain of a peculiarly light 
afh-grey colour, and a very dull earthy texture, (No. 32.) 
Between this portion of the vein and that embraced by 
the greenftone, there is a very remarkable difference, the 
. latter being of the ufual iron-grey colour, and otherwife 
perfectly characteriftic. Before it leaves the fandftone ftrata, 
it feems to contain an unufually large proportion of calcareous 
matter. This may have aided the decompofition, together with 
the moifture retained by the debris, fo lately removed from its 
furface, and which has left it in a ftate eafily affected by the 
weather. Since I commenced writing this paper, I made an 
excurfion to the fpot, and was greatly furprifed to obferve the 
devaftation of laft winter. 
Before the vein rifes above the level of the ftrata, a portion 
of it, ftill more decompofed than the reft, of a dark-purple co- 
lour, branches off; and embraces a wedge-fhaped mafs of the 
fandftone (No. 33. and 34.) indurated in a very high degree. 
Juft at the top of this indurated mafs, the whole dike changes 
its colour, and, I may alfo fay, its confiftence. It here prefents 
a light-greyifh afpect, deeply ftained, with red ferruginous 
marks, of a dull earthy texture, an even fracture, and a tolera- 
bly fine grain, (No. 35.) That portion correfponding with, 
and immediately over the included fandftone, I found much 
coarfer in the grain, (No. 36.), and in a more decompofed 
{tate ; 
* Correfponding numbers will be found in the annexed engraving, which will 
explain more fully the relative pofition of the fpecimens. 
oe 
