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 characterise. 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 of£ 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-grey ilh 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 



ftate y 



* Correfponding numbers will be found in the annexed engraving, which will 

 explain more fully the relative pofmon of the fpecimens. 



