190 THE CANADIAN NATURALIST. P Ia y 



with it ; and in the Pyrenees, La Vendee, Auvergne, the Black 

 Forest and Hungary, according to Coquand, Riviere, Rozet, Reng- 

 ger, and Beudant respectively, the gneiss and granite of these 

 countries cannot be separated into distinct formations, but form one 

 and the same mass of primitive rock. 



II. — THE HURONIAN SERIES. 



The rocks of this system, as developed on Lake Superior, 

 present at first sight rather a monotonous and uninteresting aspect 

 to the student of lithology. Large areas are occupied by schistose 

 and fine-grained rocks, the mineralogical composition of which is, 

 in the most of cases, exceedingly indistinct. These rocks are, to 

 a very large extent, pyroxenic greenstones and slates related to 

 them. On closer examination, they are found to exhibit many 

 interesting features, and it is possible to distinguish among them 

 the following typical rocks: — 



Diabase. — The granular varieties among these greenstones 

 belong to this species. It is developed at several points on 

 Goulais River, at some distance to the west of the Laurentian 

 rocks already referred to. It is usually fine-grained, pyroxene is 

 the preponderating constituent, and chlorite is present in con- 

 siderable quantity in finely disseminated particles. The felspar 

 is in minute grains, and, in many instances, it is only on the 

 weathered surface of the rock that its presence can be recognized. 

 One variety of this rock from the Goulais River has a specific 

 gravity of 3-001. Its colour is dark green, and that of its 

 powder light green. The latter, on ignition, lost 2-29 per cent, 

 of its weight, and changed to a brown colour. On digestion with 

 sulphuric acid, 22-99 per cent, of bases were dissolved from it, 

 which circumstances would seem to indicate that the felspathic 

 constituent is decomposable by acids, and is therefore, in all like- 

 lihood, labradorite. This rock is underlaid to the south-west by 

 greenstone schist, striking N. 65° W., and dipping 75° north- 

 eastward, and is overlaid by amygdaloidal diabase and greenstone 

 slates, striking N. titi W., and dipping 49° north-eastward. 

 Granular diabase is also met with a few miles higher up the river 

 from the rocks just mentioned, associated with porphyritic diabase 

 and diabase schist, the latter striking N. 55° to G5° W., and dip- 

 ping G0 Q north-eastward. Similar rocks were observed on the 

 hills between Bachewahnung and Goulais Bay, and at several 

 points on the north shore of the lake between Michipicoten 



