324 Geological Society : — 



to the Trenton limestone, both inclusive ; a group especially to be 

 found in the limestones of the Ottawa River in Canada. 



Passing across Ross-shire in a more southern parallel, from Loch 

 Duich in Kintail, on the west, to the frontier of the Old Red 

 Sandstone on the east, the general succession of rocks was de- 

 scribed to be much the same as that in North-west Sutherlandshire, 

 though there are considerable changes of lithological character when 

 the same rocks are followed southwards or south- south-west upon 

 their strike ; and the author stated his belief, that not only may the 

 regularly bedded limestones which are intercalated in the chloritic 

 and quartzose rocks of Dumbartonshire be classed with some of the 

 oldest of those stratified masses which, like the limestones of Suther- 

 land, are unquestionably of Lower Silurian age, but that the vast and 

 evidently overljnng masses of mica-schist and quartzose-gneissic flag- 

 rocks of the Breadalbane district may be some day found to be simply 

 the prolongations of the micaceous flagstones of the North-western 

 Highlands above alluded to, as overlying the quartz-rock and fossili- 

 ferous limestone : further, that in the still higher limestones and 

 schists seen on the banks of Loch Tay, we may speculate on the 

 existence of the equivalents of younger and higher strata than any 

 which are observed In the Northern Counties. 



After some observations on the truly stratified condition of these 

 micaceous and gneissose schists (younger gneiss) of the Highlands, 

 Sir Roderick proceeded to the consideration of the " Old Red Sand- 

 stone of the North-east of Scotland ; " defining the tripartite division 

 of this great series, and demonstrating that the beds with Cephalaspis 

 Lyellii and Pterygotus Anglicus of Forfarshire really lie at the base 

 of the series, and are certainly of greater antiquity than the bitumi- 

 nous fossil-bearing schists of Caithness. This division is in accord- 

 ance with the relations of the deposits of the Devonian period, as 

 seen In Devonshire and Germany ; though the lowest member of the 

 Old Red of Scotland has no representative in the Devonian rocks of 

 Russia. The Caithness flagstones were described as being In the 

 middle of the series ; whilst the underlying conglomerates and sand- 

 stones were shown to be the true equivalents of the Cephalaspis-beds 

 of Forfarshire, and of the lower cornstone-strata of Herefordshire, 

 which there graduate downwards, through the tllestones, Into the 

 uppermost Silurian rocks of Ludlow. 



The Old Red rocks of the North Highlands were described in more 

 or less detail by the author, who showed that the group, as seen in 

 Caithness and the Orkney Islands, is composed of — 1st, lower red 

 conglomerate and sandstones ; 2nd, grey and dark-coloured flag- 

 stones and schists, both bituminous and calcareous (this portion 

 being in Elginshire and Murrayshire represented by Cornstones) ; 

 and 3rd, upper red sandstones. The North Scottish Old Red con- 

 tains one great Inferior portion which has no representative In the 

 Devonian rocks of some foreign countries, though It Is completely 

 represented in all its parts in other tracts both of Britain and the 

 Continent. 



Having next described the conditions under which many of the 



