since that date appears to create a demand, and at the same time to afford the necessary means, for a fuller and more minute investigation of the subject.
The isolated rock-masses of Secondary age which occur in th_ Highlands and Western Isles of Scotland, must ever be objects of the highest interest to geologists. They are evidently the vestiges of formations once widely spread, and have escaped the extensive denudation which has to such an enormous extent destroyed the contemporary and even older deposits of the district. Preserved to our study by accidents of the most striking character, they are now found in very unexpected situations, lying in the midst of the Older Palaeozoic and often highly metamorphic rocks. On the eastern coast, as we shall see in the sequel, faults of enormous magnitude have let down these patches of Mesozoic strata among the older formations ; while on the western coast the fragments of Secondary age which had escaped the enormous denudations of the Middle Cretaceous and Older Tertiary eras, were subsequently sealed up and preserved under thousands of feet of volcanic rocks, by the wearing away of which, at a period geologically recent, they have been at a few points exposed to our observation.
These fragments of Mesozoic strata, the true nature of which was first recognized by Macculloch, Buckland, and Lyell, were in 1826-7 made the subject of careful study by the late Sir Roderick Murchison. Rightly perceiving that the nearest analogues of these rocks would be found, not in the contemporary purely marine deposits of the south of England, but among the estuarine strata of Oolitic age in Yorkshire, that distinguished geologist prudently prefaced his work by a careful study of the latter under the able guidance of William Smith and John Phillips.
If the analogies of the Scotch with the Yorkshire strata were allowed too great weight, and, owing to the difficulties of the investigation at a time when our science (and especially the palaeontological department of it) was still in its infancy, incorrect conclusions as to the exact age of many of these deposits were arrived at, every investigator of the subject will nevertheless gladly acknowledge the great value of this pioneer work of the master hand whose loss we still mourn. On every page of his memoir we recognize those powers of acute observation, of clear description, and of happy generalization which characterized the geologist who afterwards from the chaos of Transition and Grauwacke evolved the order of Siluria.
Since the date of those early researches Geology has made the most prodigious strides ; and in no department have its advances been more rapid, and the results obtained more important, than in that which relates to the study of the Jurassic rocks. The direction and tendency of modern discovery and research have been such as to invest the outlying and fragmentary Jurassic deposits of Scotland with a new and deeper interest, and to call for their examination from a fresh point of view.
By the comparison of the persevering and minute researches of
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