CHAPTER II.

The Old Red Sandstone.--Till very lately its Existence as a distinct Formation disputed.--Still little known.--Its great Importance in the Geological Scale.--Illustration.--The North of Scotland girdled by an immense Belt of Old Red Sandstone.--Line of the Girdle along the Coast.--Marks of vast Denudation.--Its Extent partially indicated by Hills on the western Coast of Ross-shire.--The System of great Depth in the North of Scotland.--Difficulties in the Way of estimating the Thickness of Deposits.--Peculiar Formation of Hill.--Illustrated by Ben Nevis.--Caution to the Geological Critic.--Lower Old Red Sandstone immensely developed in Caithness.--Sketch of the Geology of that County.--Its strange Group of Fossils.--their present Place of Sepulture.--Their ancient Habitat.--Agassiz.--Amazing Progress of Fossil Ichthyology during the last few Years.--Its Nomenclature.--Learned Names repel unlearned Readers.--Not a great deal in them, 15-34