1873 ] JTTDD — THE SECONDARY ROCKS OP SCOTLAND. 99 



since that date appears to create a demand, and at the same time to 

 afford the necessary means, for a fuller and more minute investi- 

 gation 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 mag- 

 nitude 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, Pmckland, 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 in- 

 vestigation at a time when our science (and especially the pakeon- 

 tological department of it) was still in its infancy, incorrect conclu- 

 sions as to the exact age of many of these deposits were arrived at, 

 every investigator of the subject will nevertheless gladly acknow- 

 ledge the great value of this pioneer work of the master hand 

 whose loss we still mourn. On every page of his memoir we re- 

 cognize those powers of acute observation, of clear description, and of 

 happy generalization which characterized the geologist who after- 

 wards 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 



h2 



