[Footnote G: 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 schistose system of the county, containing the fossil fish, is in geological character and position intermediate between the Old and New Red Sandstone formations, but not identical with the Carboniferous Limestone, or the true Coal Measures, although probably occupying the place of one or other of them."--p. 198.] The county of Sutherland stretches across the island from the German to the Atlantic Ocean, and presents, throughout its entire extent,--except where a narrow strip of the Oolitic formation runs along its eastern coast, and a broken belt of Old Red Sandstone tips its capes and promontories on the west,--a broken and tumultuous sea of primary hills. Scarce any of our other Scottish counties are so exclusively Highland, nor are there any of them in which the precipices are more abrupt, the valleys more deep, the rivers more rapid, or the mountains piled into more fantastic groups and masses. The traveller passes into Caithness, and finds himself surrounded by scenery of an aspect so entirely dissimilar, that no examination of the rocks is necessary to convince him of a geological difference of structure. An elevated and uneven plain spreads around and before him, league beyond league, in tame and unvaried uniformity,--its many hollows darkened by morasses, over which the intervening eminences rise in the form rather of low moory swellings, than of hills,--its coasts walled round by cliffs of gigantic altitude, that elevate the district at one huge stride from the level of the sea, and skirted by vast stacks and columns of rock, that stand out like the advanced pickets of the land amid the ceaseless turmoil of the breakers. The district, as shown on the map, presents nearly a triangular form--the Pentland Frith and the German Ocean describing two of its sides, while the base is formed by the line of boundary which separates it from the county of Sutherland.