26 THE OLD RED SANDSTONE. 
district. A deposit in one locality may be found to possess 
many times the thickness of the same deposit in another. 
There are exposed, beside the Northern and Southern Sutors 
of Cromarty, two nearly vertical sections of the coarse con- 
glomerate bed, which forms, as I have said, in the north of 
Scotland, the base of the Old Red System, and which rises 
to so great an elevation in the mountain of Morvheim. The 
sections are little more than a mile apart; and yet, while 
the thickness of this bed in the one does not exceed one hun- 
dred feet, that of the same bed in the other somewhat exceeds 
two hundred feet. More striking still— under the Northern 
Sutor, the entire Geology of Caithness, with all its vast beds, 
and all its numerous fossils, from the granitic rock of the Ord 
hill, the southern boundary of the county, to the uppermost 
sandstones of Dunnet-head, its extreme northern corner, is 
exhibited in a vertical section not more than three hundred 
yards in extent. And yet so enormous is the depth of the 
deposit in Caithness, that it has been deemed by a very supe- 
rior geologist to represent three entire formations — the Old 
Red System, by its unfossiliferous, arenaceous, and conglom- 
erate beds; the Carboniferous System, by its dark-colored 
middle schists, abounding in bitumen and ichthyolites ; and 
the New Red Sandstone, by the mottled marls and moulder- 
ing sandstones that overlie the whole.* A slight sketch of 
the Geology of Caithness may not be deemed uninteresting 
This county includes, in the state of greatest development — 
* Dr, Hibbert, whose researches among the limestones of Burdie 
House have been of such importance to Geology, was of this opinion. 
I find it also expressed in the admirable geological appendix affixed 
by the Messrs. Anderson to their Guide to the Highlands and Islands of 
Scotland. ‘No beds of real coal,’ say these gentlemen, ‘* have been 
discovered in Caithness ; and it would thus appear that the middle 
