Little Ross J Kirkcudbrightshire. 85 



which intersect each other, give the rock, when cut for build- 

 ing purposes, a beautiful variegated or veined appearance. 

 Besides these, there are brittle shales, which the action of the 

 weather has in many places reduced to a mass of disconnected 

 prismoidal fragments, that moulder away into a ferruginous 

 earth. The regular beds of greywacke are of two kinds — the 

 one blue, the other whitish, and liable to weather red, so as to 

 resemble, externally, beds of red sandstone. These two kinda 

 seem to alternate with slate-band -possessing corresponding cha- 

 racteristics. The blue alternates with dark-blue slates, hav- 

 ing glossy sides, and of a fine and sometimes silky texture ; 

 while the whiter variety alternates with greyish-white slates, 

 which weather still whiter. 



Several of the slates have the peculiarity of unconformable 

 cleavage-planes. The angles which the planes of cleavage 

 make with the line of stratification, are generally about 30 de- 

 grees. 



In some of the rocks above described, 1 have found embedded 

 small pieces of anthracite. Quartz-veins do not occur, but car- 

 bonate of lime is very common ; and sulphate of barytes is not 

 unfrequent. In one or two instances, I have found in crevices, 

 small quantities of bitumen or mineral pitch, galena, and, in 

 one instance, steatite, which shall be afterwards described. In 

 some parts also there are traces of copper-ore. 



These constitute all the stratified rocks which this small 

 island affords. Of trap rocks, we have several varieties. At 

 the beach called White Bay, and at the top of the island, 

 there are dykes of reddish coloured greenstone, in some places 

 passing into a granitic rock ; while, at others, they resemble a 

 compact felspar rock. Besides the greenstones, I have seen 

 two dykes of compact felspar base, with here and there crys- 

 tals of hornblende or augite interspersed. In a small felspa- 

 thic dyke, on the south side of the island, there are brilliant 

 specks of iron-pyrites. 



In contact with these igneous intruders, the strata have un- 

 dergone the usual changes. The greywacke ha» become 

 crystalline, so as to resemble greenstone, and the slates have 

 become, in some cases, a sort of Lydian stone. In others, they 

 are converted into flinty slates, of a yellow or cream colour, 



