448 SCIENTIFIC RECORD FOR 1883. 



annelid-markings, flags, and limestones, the latter holding Maclurea, 

 3Iurchisonia, Orthoceras, and other Lower Paleozoic forms. These uncrys- 

 talline rocks are described as the Durness or Eriboll series, and are sur- 

 mounted, in apparent conformity, by the upper division. This consists 

 of flaggy quartzose, micaceous and chloritic schists, with thick layers 

 of hornblendic and micaceous flaggy gneiss, and includes bands of dio- 

 ritic andsyenitic rock, described by some writers as igneous. There is 

 no doubt that the older gneisses are more ancient rocks underlying un- 

 conformably the fossiliferous group, the only question being as to the 

 true relation of the latter to the younger schists and gneisses which, 

 from their first appearance at their western outcrop, form an almost 

 unbroken mass, extending south and east to the central Highlands, and 

 covering an area of at least 15,000 square miles. This area includes the 

 Caledonian and Grampian gneisses of other authors, and those who, fol- 

 lowing Murchison, maintain the reality of the apparent supra-position, 

 are forced to regard the crystalline rocks of this area as altered Paleo- 

 zoic strata newer than the Durness limestone. Various hypotheses 

 have been put forth to explain the relation of these without admitting 

 such a conclusion ; while the British geological survey have accepted 

 the visible sequence, as it stands, with all its consequences. Murchison 

 noticed to the east of the fossiliferous limestone of Loch Eriboll what 

 he regarded as an upper quartzite, but this, according to Mcoll, was 

 but a repetition of that below the limestone, and was newer than the 

 upper gneiss, which he believed to be a pre-Cambrian series brought 

 up by a fault. Callaway, in like manner, maintained that there are 

 two Eozoic gneissic series unconformable the one to the other, and that 

 the fossiliferous group was laid down in discordance on both, and owes 

 its apparent infra-position to the younger gneiss to dislocations. The 

 unconformable supra-position of the fossiliferous strata to the lower 

 gneiss is, according to Lapworth, very clear. The limestone of the Dur- 

 ness series, though apparently of great thickness, and with gentle dips, 

 he finds to be made up of afew distinct lithological zones, repeated many 

 times by a series of faults or of sigmoid flexures, and to be visibly over- 

 laid at a low angle by wrinkled micaceous schists and flags, including 

 zones of gneissic and hornblendic schists. Even where faulted against 

 the limestone, this upper series appears to correspond in dip and strike 

 with the limestone series below, thus seemingly confirming Murchison's 

 view. All this is seen in the Durness area, but on proceeding to Loch 

 Eriboll, which lies in a narrow valley a few miles to the south, we find 

 on its western side the older gneiss which separates this from the valley 

 of Durness, wherein are seen only the quartzites and limestones resting 

 on this older or Hebridian gneiss. In the more eastern valley of Loch 

 Eriboll, however, while the fossiliferous rocks of the Durness group over- 

 lie on its western side the older gneiss, they are seen on its eastern side 

 clearly to overlie the newer gneiss of Murchison, upon which the quartz- 

 ite rests uncou form ably, with a conglomerate at its base. The so-called 

 upper quartzite is but a repetition of this. 



