358 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 1, 



on the opposite side of the Murray Firth. In consequence, I re- 

 explored part of my native county of Boss, and, thence passing into 

 Morayshire, there made researches in the endeavour to fix the age 

 of the yellow sandstones containing lacertine remains, and in this 

 I was zealously assisted by my friend the Eev. G. Gordon, of Birnie. 

 I followed the Old Bed deposits into Banffshire, and was satisfied 

 that the fish-bearing beds of the Spey, Tynet-burn, and Gamrie, 

 occupy, like the Caithness flags, a central position in the Old Bed 

 series, and do not constitute the lower division, as had been pre- 

 viously stated in all geological works. 



Lastly, in examining the same series as exhibited on the S.E. of 

 the Grampians, I was convinced that the grey flagstones of Arbroath 

 and Dundee, and the flanks of the Sidlaw Hills, there form the base 

 of the same natural group, and that the Bed Sandstone of Perth 

 graduates up into those yellow sandstones of Fife, which, being 

 charged with certain fishes peculiar to the deposit, are distinct, on the 

 one hand, from the central or Caithness beds of Old Bed Sandstone, 

 and from the lowest beds of the Carboniferous System of Scotland on 

 the other. The following observations will not be given in the order 

 of my tours, but by beginning with the oldest rocks and ascending 

 to the youngest, as in preceding communications. 



In offering this general view, I beg my associates to dwell chiefly 

 on the facts adduced, and not to judge a memoir which relates par- 

 ticularly to the northernmost counties of Scotland, with a few allu- 

 sions to the Orkney and Shetland Islands, by the incidental expres- 

 sion of my own speculative opinion respecting the more southern 

 parts of the Highlands. Let me add, however, that even that addi- 

 tion has not been solely drawn from the few leading data to which 

 allusion is here made, but is the result of several visits to different 

 parts of the country. My companion in the year 1827, Professor 

 Sedgwick, will recollect how, on the summit of Ben Wyvis, we then 

 regarded its micaceous and gneissose flagstones with little other in- 

 terest than as parts of those rocks out of whose debris the lower con- 

 glomerate of the Old Bed Sandstone had been formed. Little did we 

 then anticipate that in a few years we should both be actively engaged 

 in the classification of various formations of much higher antiquity 

 than the Old Bed Sandstone, then regarded by us with such venera- 

 tion, and which by their order and organic remains would enable 

 geologists to decide upon the real age of the stratified crystalline rocks 

 of the Highlands ! 



In concluding this introduction, which may at the same time be 

 considered a resume of the facts to be detailed in the memoirs which 

 foUow, a few words only need be said upon the great change which 

 must now be made in aU geological maps of the Highlands of 

 Scotland. The gneissose and quartzose rocks, limestones, chloritic 

 schists, micaceous schists, indeed, may remain as lithological sub- 

 divisions of groups ; but the order of the legend attached to Maccul- 

 loch's Geological Map of Scotland must be essentially changed, for 

 Lower Silurian fossils are now known to occur in rocks near the 

 bottom of the primary crystalline scale. , 



