1858.] MURCHISON NOETHEEN HIGHLANDS, ETC. 359 



Not pretending to define the exact boundaries of the formations as 

 now divided, I have still endeavoured to colour roughly a little geo- 

 logical map* of the Northern Counties and the Orkney Islands 

 (PL XII.). In doing this, I have separated the old or fundamental 

 gneiss from the younger quartzose and Lower Silurian series, with 

 which Macculloch had merged it, by interpolating a great formation 

 of Cambrian age, and have shown that the true Old Eed Sandstone, 

 overlying all those rocks, is marked by that triple division which so 

 distinguishes it in Caithness and the Orkney Islands. 



In treating of the Old Eed Sandstone, I trust that the endeavour 

 which I have made to demonstrate that the strata with Cephalaspis 

 Lyellii, Pterygotus Anglicus, and ParTca decipiens, which really lie 

 at the base of all that series, are certainly of higher antiquity than 

 the bituminous fossil-bearing schists of Caithness, vrill meet with 

 the approbation of my associates. 



The separation of the older and younger gneiss is, of course, easily 

 effected in those tracts, where, as along a large portion of the North- 

 west Coast, the great intervening conglomerate and sandstone of 

 Cambrian age, as well as certain Lower Silurian rocks, occur ; but 

 there are doubtless more points than are known to me, in the in- 

 terior or eastwards, where the old gneiss may be at once covered by 

 younger rocks without the intervention of any such conglomerate or 

 sandstone. In short, the general section (fig. 1) is to be considered 

 as the diagrammatic sketch of my own views respecting the true 

 order of succession, founded on data obtained by other inquirers as 

 well as by myself. 



The reader will well understand that some such view as is here pre- 

 sented is absolutely called for in order to clear up the scepticism which 

 prevailed in the minds of the most eminent geologists respecting all 

 the so-called Transition rocks before the new classification, as esta- 

 blished upon superposition and organic remains, was propounded. 

 So strongly was this felt, that in his last work, 'A System of Geology,' 

 published in 1831, Macculloch thus writes : — " As the nature and 

 boundaries of this class [the Transition rocks] have never yet been 

 defined or proved, I have not given it a place in this work among 

 the facts of geology. Yet if it really should be established by fiitui'e 

 and better observations, I shall owe the science an apology to which 

 I cannot yet consider any geologist entitledf." 



Fundamental Gneiss. — The most ancient stratified rock in Scot- 

 land, and, as far as I know, in the British Isles, is that gneiss which 

 is exhibited in the north-western shores of Eoss and Sutherland, 

 where it forms the rugged basement of the whole stony superstruc- 

 ture, and has been well described by various authors, fromMacculloch 

 and Jameson to Cunningham. This rock is, even mineralogicaUy, 

 distinguishable from a younger metamorphic rock, which has also 



* This map will be issued in a subsequent Number of the Journal, it being my 

 intention to revisit the Highlands this summer, in order to satisfy myself still 

 fiu-ther on some doubtful points, — particularly in respect to the Reptihferous 

 sandstones of Moray. 



t Oj). cit. vol. i. p. 469. 



