The geology of the northern division of Scotland is, almost in every particular in the series of rocks that have been described, the counterpart of the southern, which now falls to be noticed. The fossils so richly imbedded in the former are here repeated, more sparingly in some, more abundantly in other families, and, in several instances, in the introduction of entirely new forms of organic life. Along the west and south border counties, the granites, with their associated crystalline group, are sparingly developed, stretching, at intervals, from the island of Arran through Galloway and Kirkcudbright into Dumfries-shire. The silurians follow in their order of superposition, occupying an extensive area from sea to sea across the island. The devonian system, chiefly in the upper and middle beds, wraps round the base of the older formation, and rests unconformably on its highly-inclined strata. The carboniferous deposits are widely distributed, some in isolated basins, and enveloped by the old red, and pregnant all of them with the fossils of the period. The ignigenous rocks, the traps and porphyries, are also very abundant, some in the form of detached cones, some in extensive ranges, and all demonstrative of their character as the agents that have lifted up, disrupted, and twisted the strata of the district. In passing over this section of our course, it will not be necessary, therefore, to dwell in any minute or lengthened descriptions. I. The geological student, in commencing his researches at Edinburgh, is immediately arrested by the more prominent objects that everywhere rise into view—the Castle Rock—the Calton Hill—Salisbury Crag—Arthur’s Seat—and the Pentlands. A wondrous, glorious scene, every one involuntarily exclaims, upon reaching any of these heights, thrown, as if by the hand of an enchanter, in and around this lovely city. Geology here has its favorite residence—the birth-place and cradle of the HUTTONIAN THEORY—Arthur’s seat there to attest its truth. What a history of bygone times recorded in these two words! What a revolution produced in the sentiments of mankind as to the science of world-making! And, still more, how deeply were men’s minds agitated, and the foundations of religious truth stirred, by the novel views which were then announced! The assumption lying at the foundation of the rival, or Wernerian theory, is, that the materials of which the various strata of the globe consist were originally dissolved or suspended in water: they were thus in a condition to assume any form which their physical qualities and the laws of matter might determine; and, accordingly, in this fluid menstruum they were consolidated into various combinations, partly by means of crystallization, and partly by mechanical deposition. The Huttonian theory, on the other hand, employs the force of subterraneous fire as its principal machinery, which is placed at immense depths,