and Relations of the Frontier Chain of Scotland. 255 



peared to belong to a deposit of the age of the Wenlock 

 shale. Knowing this apparently decisive zoological evidence, 

 the author went round Barrow Head and some other parts 

 of the neighbouring coast, in the hopes of seeing some phy- 

 sical evidence for the existence of an upper group ; but he 

 was disappointed. The rocks along the neighbouring coast 

 have the average character of the rocks he includes in the 

 second group of the chain. They are very highly inclined, 

 and thrown into great undulations, and the Balmae group is 

 involved in these undulations without any material change 

 of structure that (independently of fossil evidence) would in 

 any way suggest the existence of a new and upper group. 

 A little way along the coast towards the N.E,, these rocks 

 are overlaid by the old red sandstone ; and still further to 

 the N.E., beyond the old red sandstone, calcareous bands 

 appear among the slate rocks, but apparently without fossils. 



III. — Concluding Remarks. 



In concluding this summary the author remarks, that the 

 chain above described is the true connecting link between 

 the older rocks of England and Scotland. In comparing it 

 with the Grampian chain, we have hitherto been deprived of 

 all fossil evidence ; but a careful examination of the zone of 

 unaltered slates, that is packed between the metamorphic 

 slates of the Grampians and the old red sandstone, might 

 lead, perhaps, to the discovery of graptolites ; and graptolites 

 are found in all the groups of the frontier chain, from the 

 highest to the lowest. 



Granite breaks out in (at least) five places in the frontier 

 chain. Three are laid down (though very inaccurately) in 

 M'CuUoch's map ; a fourth was found by Mr J. C. Moore, on 

 the western shore of the Mull of Galloway ; and a fifth mass 

 (as shown by Mr Stevenson) breaks out to the north of Dunse, 

 near the junction of the greywacke and the old red sandstone. 

 It is clear, that these masses form no mineralogical centre, and 

 that we have no reason to attribute the great undulations of the 

 chain to their immediate agency, but to some more widely act- 

 ing cause. Enormous masses of trap, sometimes associated 

 with trappean breccias and conglomerate (and generally un- 



