192 THE CANADIAN NATURALIST. , [May 



latter rocks to those of a finer grain, the same name's are perhaps 

 applicable. But since this is not always the case, it would seem 

 advisable to make use of other terms for them until their compo- 

 sition is more accurately determined. The names aphanite and 

 aphanite slate have been applied to rocks such as these, but since 

 the former term has been applied by Cotta to compact melaphyre, 

 it would seem better for the present to continue the use of the 

 other terms, compact greenstone and greenstone slate, especially 

 since the signification of the first of these has been so limited by 

 Naumann as to denote pyroxenic greenstones only, thus distin- 

 guishing them from the hornblendic greenstones or Diorites. 

 These pyroxenic greenstones, or fine-grained diabases, frequently 

 contain more chlorite than the coarser-grained varieties. They 

 are very frequent on the Goulais River, in the district between it 

 and Bachcwahnung Bay, and in the neighbourhood of the 

 Bachewahnung Iron Mine. One specimen from a point four 

 miles north-east of Goulais Bay yields 2144 per cent, of bases to 

 sulphuric acid. Its powder is dark green, changing on ignition to 

 dark brown, and losing 1-72 per cent, of its weight. These 

 greenstones are seldom destitute of iron pyrites. Quartz never 

 occurs in them as a distinct constituent, and even in veins it is 

 rare ; but there are a few occurrences of greenstones which are 

 lighter in colour, more siliceous, and harder than others, and 

 which have possibly become so by contact with quartzose rocks. 

 On the other hand, they are frequently found impregnated with 

 calcareous matter. By assuming a schistose structure, these 

 greenstones often graduate into greenstone slate, an apparently 

 homogeneous rock, generally of a dark greenish grey colour and 

 slaty texture. The latter character is sometimes so marked, that it 

 becomes difficult to distinguish it from clay slate. The greenstone 

 slates however, would seem to differ from the latter rock in the small 

 quantity of water which they contain, their generally higher 

 specific gravity, and in their yielding nothing which would form a 

 o-ood roofing slate. On the other hand, they are related to the 

 greenstones and diabase schists not only by gradual transition, but 

 in some of their physical characters. For instance, a greenstone 

 slate from Dog Biver, on the north shore, of a dark grey colour, 

 has a specific gravity of 2-738, and loses 1-62 per cent, of its 

 weight on ignition, in which operation the colour of its powder 

 changes from a greenish white to a decided brown. It yields to 

 hydrochloric acid 16 --14, and to sulphuric acid 10-29 of bases. 



