106 ᾿ REPORT—1850. 
§ 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‘Culloch’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 mine- 
ralogical centre, and that we have no reason to attribute the great undulations of the 
chain to their immediate agency, but to some more widely acting cause. Enormous 
masses of trap, sometimes associated with trappean breccias and conglomerate (and 
generally unmarked on the geological’ map of Scotland), break out in various parts of 
the chain from one end of it to the other, and sometimes pass into a form of serpen- 
tine. Many dykes, both felspathic and augitic, are seen in the cliffs and quarries ; 
and we occasionally find bands of porphyry alternating with the slates; but in no 
instance did the author find any good example of that singular combination of 
porphyry, trappean shale (schaalstein), and slate, which gives such an impress to 
the higher mountains of Cumberland. 
This fact explains the great difference in the features of the neighbouring Scottish 
and Cumbrian chains, and may perhaps help us in explaining the almost entire 
absence of slaty cleavage in the former. 
The lowest fossils in the two chains appear to be graptolites. To this fact the 
author’s attention was often called ; but he does not pretend to identify the pyritous 
Moffat slates with the Skiddaw slates. The present evidence is not sufficient to bear 
out such a conclusion: and the whole Moffat group is only provisional. 
On the second group he, from defect of evidence, makes no comparative remarks. 
The South Girvan group is compared with the Bala and Coniston groups, and the 
Stinchard limestone with the Bala and Coniston limestone. The North Girvan group 
is compared with the grits and shelly sandstones which overlie the Llandeilo lime- 
stone. The eyidence for these conclusions will be found in the following list of 
fossils. 
The Balmae group is arranged provisionally as the fifth and highest, on evidence 
formerly laid before the Geological Society of London; but from physical evidence, 
as well as from the list of fossils which (with the kind assistance of Messrs. Under- 
wood and Fleming) he derived from the shores of Kirkcudbright Bay, the author 
would rather place this Balmae group on a lower parallel, and perhaps lower than 
the Stincher limestone. 
Lastly, the author remarks, that the Grampians had probably their greatest ele- 
vation after the period of the old red sandstone, which is of enormous thickness and 
thrown off vertically from the older rocks of the chain; but the undulations and 
principal elevations of the frontier chain were produced before the deposit of the old 
red sandstone. For the old red sandstone, with a comparatively low angle of in- 
clination, rests on the edges of the older rocks, and runs up the deep bays and hol- 
lows of the frontier chain; and (as shown by Mr. Stevenson) in one or two in- 
stances passes almost continuously through it. Similar phenomena are seen among 
the mountains of the great Cumbrian group, which were probably elevated coutem- 
poraneously with the frontier chain of Scotland. 
This chain does not appear to have undergone any great elevation during the whole 
carboniferous epoch; for the new red sandstone, after this epoch, plays the same 
part that was before played by the older red sandstone, viz. it rests unconformably on 
the older rocks and runs up their deep indentations and hollows, sometimes so as 
almost to traverse the whole chain, a fact which has led to much misapprehension 
and many false colours on the Scotch geological map on which the old and new red 
sandstone have often been confounded. 
