36 



THE r.AURENTIAN. 



Ordovician. 



Caradoc and Bala, with Snowdon 

 felsites and asli-beds, Coniston and 

 Knock Series. 



Great felsite and trap-ash Series 

 of Borrowdale (Ward). 



Lower Llandeilo flags and shales, 

 Arenig Scries, Skiddaw slates, &c. 



Upper Cobeqiiid Sei'ies, slates, 

 felsites. quartzites, and greenstones. 

 Ordovician of Western and Central 

 New Brunswick. 



Lower Cobequid Series, felsites, 

 porphyrites, agglomerates, and mas- 

 sive syenite of Cobequids, Pictou, and 

 Cape Breton ? 



Middle Graptolitic or Levis Series 

 of Quebec and North New Brunswick, 

 part of Cape Breton Series ? 



Cambrian. 



Tremadoc slates and Lingula-flags. 



Menevian and Longmynd Series, 

 Harlech grits, and Llanberis slates. 



Caerfai Group of Hicks. 



Matane or Cape Rosier Graptolitic 

 beds. Mire and St Andrew's Channel 

 Series in Cape Breton ? 



Acadian Series of St John, New 

 Brunswick ( Pai-adoxuhs-hedn). Quart- 

 zite and slate of Atlantic coast of Nova 

 Scotia. 



Olenellus beds and Basal Cambrian 

 of Southern New Brunswick. 



Huronian. 



Pebidian Series (Hicks 

 felsite, chlorite-schist, and Serpentine. 



contaming 



Huronian felsites, chloritic and 



epidotic rocks of Southern New 



Brunswick, Yarmouth, and of Cape 

 Breton in part. 



Laurentian. 



Older gneisses of Scotland and of 

 Scandinavia, Dimetian ? 



Gneiss, quartzite and limestone of 

 St John, Portland Group, gneiss of 

 St Anne's Mountain. 



The question of Palaeozoic climates in the northern hemisphere 

 has some bearings on the subjects discussed above, and is well 

 illustrated by a map of the Arctic districts of Canada recently issued 

 by the Geological Survey.* From this it appears that there are no 

 indications of a warm climate in the Arctic basin up to the close of 

 the Cambrian. The later Ordovician and the Silurian were, however, 

 .signalized by the deposition in the Arctic seas of thick and extensive 

 organic limestones, holding fossils comparable with those of the 

 temperate regions at the same time. The Lower Erian may perhaps 

 indicate a short relapse to cold ; but in the Upper Erian and Lower 

 Carboniferous we have warm seas tenanted by marine animals and 

 a rich land-vegetation appearing both in the Arctic islands of 

 Canada and in Spitzbergen. The Upper Coal-formation and the 

 Permian and Trias indicate a return of cold, and the temperature 

 seems to increase in the Jurassic, attaining its maximum in the later 



* " Geology of Northern Canada," Dr G. M. Dawson, 1887. 



