662 J. W. JTJDD ON THE SECONDABY EOCKS OF SCOTLAND. 



of certain other deposits of great interest which certainly fell under his 

 notice. In spite of these drawbacks, however, Murchison's labours 

 were of the greatest importance and value, in establishing the exist- 

 ence and order of succession of the Liassic and Oolitic strata of the 

 Western Isles. 



Up to the year 1870, when I commenced my researches in this 

 area, no Secondary rocks other than those of Jurassic age, had 

 been certainly proved to exist in the Western Isles of Scotland. 

 During the last seven years, however, I have been engaged in working 

 out the relations and order of succession of the various scattered 

 fragments of fossiliferous strata which underlie the enormous 

 masses of Tertiary lavas, and have been gradually led to the following 

 conclusions : — At the base of these sedimentary rocks, intercalated be- 

 tween the Palaeozoic schists and the Tertiary lavas, occur strata con- 

 taining the well-known plants of the Coal-measures, and undoubt- 

 edly representing the Carboniferous system — a system hitherto sup- 

 posed to be wholly absent from the Scottish Highlands. Above these 

 Carboniferous strata are found a great development of the Mesozoic 

 formations, the united thickness of which could have fallen little, if 

 at all, short of a mile. In this vast mass of stratified rocks are in- 

 cluded very highly interesting representatives of all the great 

 Secondary systems, with the exception of the Neocomian ; we have 

 extensive deposits belonging to the Poikilitic, the Jurassic, and the 

 Cretaceous (the first and last of these being now described for the 

 first time as existing in this area). Further we find that grand un- 

 conformities exist in the midst of this series, and indicate the lapse 

 of great periods, which were not epochs of subsidence and of sedi- 

 mentary deposition in the area which we are describing. 



My object in the present paper will be to endeavour to reconstruct, 

 from the scattered and fragmentary records in this area, the history 

 of the succession of geological events during the vast periods of the 

 Mesozoic epoch. I had originally intended to supplement this 

 account of the stratigraphical succession of the deposits with descrip- 

 tions of such new fossils as have come under my observation during 

 the prosecution of my task ; but I now find that this would increase 

 my paper to inordinate proportions, and I have therefore determined 

 to postpone this part of my work ; and I do so the more readily, as I 

 find the steadily increasing number of students of palaeontological 

 geology in Scotland happily promises to relieve me of this part of 

 my task altogether. 



The researches on which this paper is founded have occupied 

 much of my time and thought during the last seven years ; and in 

 my last visit to the district, during the summer of 1877, with a view 

 to the final revision of my notes previous to their publication, I had 

 the pleasure of being accompanied and assisted by two students of the 

 Eoyal School of Mines— Dr. J. Taylor Smith and Mr. E. D. Oldham, 

 the former of whom was with me during a great part of the 

 autumn's work. 



