130 Hevieics — Prof. GeiJde^s Geological Map of Scotland. 



and almost invisible washes placed side by side witli glaring 

 splashes of brilliant paint, which disfigure even some of the best of 

 the Survey maps. Here, while the brighter colours mark at a glance 

 the localities of the igneous interruptions to the general continuity 

 of the more soberly tinted aqueous deposits, the general tone ^2 the 

 map is quiet and subdued. Not a single detail is obscured, aid the 

 general effect is grateful and pleasing to the eye. 



In indicating the main points of advance made by the present 

 map upon its predecessors, we shall pass over the earlier geological 

 maps of M'Culloch and Nicol, and restrict our observations to a 

 comparison with the small map of Murchison and Geikie already 

 referred to, and which was professedly the first sketch for the geolo- 

 gical map of which the present publication is the completed design. 



Beyond the more exact delineation of the boundaries of the 

 Lewisian gneiss and the Torridon sandstones, we are presented with 

 nothing new in the fundamental rocks of Sutherland and Ross. The 

 larger scale of the map, however, not only admits of the more precise 

 definition of the limits of the various divisions of the Highland 

 metamorphic rocks, but a vast amount of new detail is inserted. In 

 the all-important area of the North-west Highlands the great Durine 

 band of quartz-rock is seen to be by no means so broad or so in- 

 variable a geographical feature in that district as appeared from the 

 earlier map, nor do its two limestones always appear to occupy the 

 same relative places in the general series. 



The quartz-rocks which imbed the classic limestones of Glen Tilt 

 are no longer figured as forming a vast elliptical island in the meta- 

 morphic schists, but are seen to be extended far to the north in the 

 wilds of Badenoch, and to form four narrow strips running through 

 Banff and Aberdeen to the shores of the German Ocean. On the 

 other hand, although the line of anticlinal axis, running from Loch 

 Tay to the mouth of Loch Fyne, is distinctly laid down, the great 

 sheet of supposed quartz-rocks which formerly accompanied it, and 

 was believed to be prolonged to the Mull of Cantire, is now coloured 

 as of later age, and the limestones which partially defined its upper 

 boundaries are now theoretically placed at the summit of the suc- 

 ceeding schistose formation, instead of at its base. 



The clay-slate formation of the older geologists again finds its 

 special place and colour upon the map, and we recognize with 

 something akin to pleasure our old and well-nigh forgotten ac- 

 quaintance, in its original position along the southern margin of the 

 Hio-hlands. Its geologic place, however, appears to be to the full 

 as difficult of definition as ever. If we may trust the Argyllshire 

 sections and the legend on the map, it must be separated from the 

 basal quartz-rock formation by an enormous series of micaceous 

 schists. If the Banffshire sections are to guide us, it must repose at 

 once upon the quartz-rock formation, without the intervention of 

 any schistose beds whatever. 



Turning next to the unaltered deposits of the Southern Uplands, 

 we notice that the Upper Silurian colouring has been very properly 

 extended to the schists and flagstones of Langholm and Stobo, 



