1858.] MURCHISON NOETHEEN HIGHLANDS, ETC. 417 



day we were necessarily unacquainted with the numerous ages diuing 

 which the red sandstones and conglomerates of Scotland had been 

 accumulated. It has, in fact, been ascertained that the conglomerate 

 and sandstone of the West Highlands, which then passed for Old 

 Red Sandstone, is of Cambrian age, and hence it foUows that the red 

 deposits lying unconformably upon those rocks may belong to the 

 Old Red as well as to any other overlying deposit. 



Of the Scottish red sandstones and conglomerates we may now 

 indeed reckon the following : — 



1st. Cambrian, or that of the N.W. Highlands. 



2nd. Great Lower Silurian conglomerates of Ayr and Wigton. 



3rd. Old Red base, underlying the Caithness Flags. 



4th. Old Red summit, overlying the Caithness Flags. 



5th. Carboniferous varieties. 



6th. Permian conglomerates and sandstones of the S.W. of Scot- 

 land — -Dumfries, Ayrshire, and the Isle of Arran. 



7th. Red and green marls and sandstones, supposed to be of Tiias- 

 sic age, as seen in small detached portions. 



Lias and Oolitic Deposits. — These Secondary deposits, which, as is 

 well known, occupy large breadths in the Hebrides and are more 

 sparingly distributed along the N.E. of Scotland, are now much 

 better known than when I first endeavoured to make Enghsh geolo- 

 gists conversant with them by comparing them with their best types 

 in England *. They will be again alluded to in the following memoir. 



The late Hugh MiUer has since expatiated on their fossil contents 

 and peculiarities on both shores of the Highlands ; whilst the breccias 

 of the Oolite of Brora near Helmsdale have afforded to his scrutiny 

 a multitude of beautiful fossil plants, which complete the resemblance 

 of these northern deposits to their equivalents on the east coast of 

 Yorkshire. The intercalation of freshwater beds in these Oolites, of 

 which I only obtained a glimpse thirty years ago, has since been 

 matured on the east coast by the late Mr. Robertson f, as well as by 

 the late Edward Forbes on the Isle of Skye J. As respects the Liassic 

 and OoKtic succession of the Hebrides, Mr. Geikie§ has recently mtch 

 improved our knowledge of the relations and boundaries of aU the 

 rocks in parts of the highly diversified Isle of Skye. 



These subjects are indeed beyond the gist of the present memoir, 

 and they are here merely touched upon in order to unite in one 

 general view the whole of the ascending order of all the stratified 

 deposits which really exist in the Northern Highlands. 



Lastly, above all these lie those grand superficial accumulations of 

 drift and huge erratic blocks, which, whether studied with reference 

 to their glacial origin, or as connected with raised beaches of different 

 levels, open out some of the most exciting subjects with which the 

 geologist can grapple ; they are, however, unconnected with my pre- 

 sent object. 



* See Trans. Greol. Soc. Lond. 2nd ser. vol. ii. p. 293. 



t Proceed. Geol. Soc. vol. iv. p. 173 ; and Quart. Journ. Geol. Soc. vol. iii. p. 113. 

 X See Quart. Journ. Geol. Soc. vol. vii. p. 104. § Ibid. vol. xiv. p. 1. 



2h2 



