1849.] NICOL ON THE SOUTH-EAST OF SCOTLAND. 55 



found in Ireland. These new discoveries therefore form a very satis- 

 factory confirmation of Mr. Salter's identification of the trilobites and 

 shells of the "Wrae limestone vrith those of the Tyrone beds. 



The Grieston slates often contain small fragments of anthracite, 

 and a considerable amount of this substance was found some years ago 

 in the Cadon Bank, a hill about a mile distant, forming an irregular 

 bed or vein among the grejr^vacke strata. It is very impure, and 

 burns with much difficulty, so that even after being exposed for some 

 time to the flame of the blowpipe, the form of the mass is little altered. 

 The strata in which it occurs have been much disturbed and affected 

 by igneous action, being intersected in one place by a vein of amyg- 

 daloidal greenstone, whilst the top of the hill is formed of red felspar 

 porphyry. In the ashes of this anthracite I have observed tubular 

 fibres under the microscope, so that no doubt can be entertained of its 

 organic nature. It thus proves that plants existed even in these early 

 periods, in sufficient abundance to produce thin beds or seams of coal. 

 In the Grieston slates some markings occur which may have been 

 algse, but the structure shown in the ashes of the anthracite would 

 rather indicate a higher class of vegetation. 



About three miles to the north-east of the Grieston and nearly m 

 the strike of the beds, I also succeeded in obtaining a few specimens 

 of fossils. They were found on Torysknies, a hill belonging to that 

 group, in which, as the map will show, igneous action has chiefly pre- 

 vailed in this district ; the felspar porphyries decreasing in amount 

 with the distance from it. The summit of the hill is formed of por- 

 ph3Ty, but the declivities consist of hardened slates, often almost 

 crystalline in texture and closely resembling clinkstone. They con- 

 tain much iron, and seem so altered by the connected igneous rocks, 

 that the preservation of fossils was very unexpected, and proves the 

 extreme difficulty of destroying organic forms when they are once im- 

 bedded in the solid stone. 



The discovery of these remains in the prolongation of the former 

 strata, shows that the fossiliferous beds are probably persistent for 

 considerable distances, and may thus aid us in working out the suc- 

 cession of these accumulations. It was also interesting on another 

 account. About 500 yards south of the Grieston slates, a bed of red 

 felspar porphyry is seen running nearly parallel to the slates, and may be 

 traced in the same position relative to their outcrop for about a mile 

 westward, A similar rock occurs at interv^als for nearly four miles in 

 the same line, but seems to disappear with all the rocks of this class 

 before reaching the valley of the Yarrow. On the east I have traced 

 this, or a similar vein, at short intervals, cropping out on the sides of 

 the hills or in the beds of the streams to a point north of that where 

 the graptolites occur : at this place, however, the vein appears to have 

 divided into two beds about fifty yards apart. This vein seems thus 

 continuous for nearly eight miles in one direction, and runs generally 

 parallel to the strata. This parallelism is, however, not complete, as 

 it is in one place to the south, in the other to the north of the fossili- 

 ferous beds, and has therefore intersected them in the interval*. 



* A still stronger proof that some at least of these felspar rocks are not con- 

 temporaneous with the strata, but truly injected masses or dykes, is furnished by 



