Heviews — Prof. Geildes Geological Map of Scotland. 131 



whicli lie to the south of the Hawick rocks, and agree in every 

 respect with the Coniston Flags and Grits of the North of England. 

 Although the ofiScers of the Survey have satisfied themselves of the 

 existence of several important divisions in the so-called Llandeilo 

 series of greywackes whose contorted beds floor almost the whole of 

 the Uplands, no attempt has been made to define their limits upon 

 the small scale of this map. A new and most valuable feature is 

 seen, however, in the insertion of the main lines of black shale in 

 the central districts and Galloway, but no distinction is made 

 between the so-called Upper and Lower groups. These omissions 

 are compensated to a certain extent by a marginal section through 

 the central portion of the Silurians from the Cheviots to Tinto. 

 Here the Ardwell or Hawick rocks are figured as being covered un- 

 conformably to the south by the Eiccarton Beds of the Upper Silurian, 

 but the hypothetical nature of the break is carefully indicated 

 by a note of interrogation. The thin deposit of the Moffat Shales is 

 shown as reposing upon the Ardwell Beds and passing below the 

 Qneensberry Grits to the south of Ettrick Pen, and on both slopes 

 of the Moffat Valley. It is a little awkward for this theory that 

 there are no black shales in this position to the south of Ettrick Pen, 

 nor for many miles to the north-east ; while the extension of this 

 strike to the south-east would carry us deep into typical Ardwell 

 Beds. At the same time the black bands on the opposite side of the 

 Moffat Yalley happen to be the most easily demonstrated anticlinal 

 forms in the whole of the Moffat district. 



The numerous patches of calcareous grit and conglomerate with 

 Caradoo and Llandovery fossils are shown by a distinct colour upon 

 the map. In addition to the typical area of Duntercleuch, the corre- 

 sponding strata of Kilbucho, Wrae Hill, Moniave, etc., are marked as 

 of Caradoc age. In the section they are represented as unconformable 

 upon the Llandeilo greywackes. This classification has been 

 extended to the interesting Girvan area. The great fault formerly 

 supposed to cut off the Llandeilos of the Uplands from the Girvan 

 beds is omitted, and the Caradoc tint is restricted to the two small 

 and possibly unconformable patches of Assel and Craighead. 



A special and highly interesting feature of this map is the develop- 

 ment and classification of the rocks which lie between the summit 

 of the true Upper Silurian and the acknowledged base of the Scottish 

 Carboniferous Limestone. The long line of fault throwing down 

 the Eed Sandstone of Strathmore from Stonehaven to Loch Lomond 

 is here, for the first time, shown in its true position ; and the 

 irregular boundary of the basal conglomerate upon the clay- slates 

 of the southern margin of the Highlands is carefully shown from 

 the work of Professor Geikie and his assistants. The more im- 

 portant results of the recent work of the officers of the Survey in 

 Forfar and Kincardine are filled in. Special care has been bestowed 

 upon the strangely interlaced group of felstones, ashes, and sand- 

 stones of the Sidlaws, Ochils and Pentlands, every conspicuous 

 rock-sheet being laid down with painful minuteness. 



In accordance with the views broached by Professor Geikie in 1876 



