Sandstone in the County of Forfar. 115 



Kirriemuir, about half a-mile above the bridge of New Mill. 

 The course of the river then is about N. W. and S. E. cutting 

 at right angles the general direction of the strata. The first rock 

 which rises precipitously on both its banks on the northern 

 extremity of the ravine, is an unstratified porphyry, having 

 a base of clay-stone, in which are imbedded crystals of felspar 

 and hexagonal mica, small particles of quartz, and sometimes 

 spots of soft white talc. Angular fragments of green foliated 

 talc, undulatingly curved, are frequent in it. The rock is of 

 a brownish or purplish red colour. A porphyry, exactly re- 

 sembling it in character, is seen in a similar position near Lin- 

 trathen, and on the Isla, near the Falls of the Reekie Linn, 

 also on the North Esk, where Colonel Imrie has described 

 it. * It is sometimes very granitiform, and, in one instance, 

 I found, near Lintrathen, large boulders of it in the field, in 

 which rounded pebbles of granite were imbedded, -f- 



This porphyry continues on both sides of the river for seve- 

 ral hundred yards, and is seen followed on the left bank by a 

 conglomerate. The relations of the conglomerate with the 

 porphyry are obscurely seen, as the fragments of the decom- 

 posing porphyry, fallen from the cliff above, have covered and 

 concealed the junction, but it is evident, that the edge of the 

 porphyry, as it thins off, overlies a portion of the conglomer- 

 ate. The conglomerate contains pebbles" of quartz and mica- 

 shist in a base of sandstone, sometimes highly ferruginous, 

 sometimes quartzose. Its dip, as far as can be ascertained, is 

 northerly, whereas the sandstone, which immediately follows 

 it, is inclined in a contrary direction, at an angle of 44 to 

 S. S. E. The strata must here have suffered great disturbance. 

 The sandstone, for the first twenty yards, approaches to a 

 shale ; it is of a deep ferruginous brown colour, fine-grained, 

 and very thinly laminated, being full of minute plates of mica, 

 disposed parallel to the dividing surfaces. The sandstone 

 above mentioned, after extending twenty yards, becomes grayer, 

 and less argillaceous ; it is still thinly laminated, and dips also 



* Transactions Royal Society Edinburgh, vol. vi. p. .1. 

 t Specimens of tlie various rocks, mentioned in this paper, are deposited 

 in the Museum of the Geological Society of London. 



