Sandstone in the County of Forfar, 123 



side, in the parish of Kingoldrum. The small burn, in whose 

 channel it is here obscurely exposed, falls afterwards into the 

 Backburn. The rocks, which are there clearly seen associated 

 together, are greenstone, with serpentine, containing much 

 dolomite, and a red indurated "rock abounding in brown spar. 

 A little higher up the burn, as on the Carity, the claystone 

 porphyry appears, which must not be considered as having 

 any connection with the serpentine. If we continue our line 

 to the south-westward for about two miles, we arrive at the 

 ravine through which the Melgum flows, when the serpentine 

 is not recognizable, unless it be considered as represented by 

 the great dike of greenstone which crosses that river imme- 

 diately below the mill of Shanalaw. 



But I am aware, that great caution must be used in the at- 

 tempt to identify these dikes, as we have seen that there is on 

 the Carity a dike of greenstone parallel to the serpentine. 

 Proceeding about a mile and a half farther, a fine section of 

 the rocks is presented on the precipitous cliffs which rise on 

 each bank of the Isla, a short distance below Peel. There a 

 dike of greenstone crosses the river, possessing for the most 

 part the ordinary characters of that rock, but in some places 

 intermixed with carbonate of lime, and assuming then a finer 

 texture, and appearing not very unlike much of the English 

 black compact mountain limestone. Its junction with the 

 strata through which it passes is only seen on its northern 

 side, on the left bank of the Isla, and the phenomena whicli 

 attend it are exactly analogous to those already described on 

 the Carity. Next to the greenstone is a parallel mass of al- 

 tered indurated rock, much charged with brown spar, and in 

 parts calcareous, then a mass of conglomerate, in which the 

 quartz pebbles, before alluded to, are split, and reunited by 

 ferruginous matter. Without advancing any theory to ac- 

 count for this curious fact, I may be allowed to say, that the 

 rounded fragments of quartz appear exactly as if they had di- 

 vided upon being heated, and had only been prevented from 

 flying asunder by the matrix in which they are imbedded. 

 Beyond the conglomerate is sandstone, very ferruginous, hard- 

 ened, with a fracture sometimes conchoidal, and traversed by 

 veins of brown-spar. It dips towards the dike, and its strati- 



