104 COLIiMAN ON THE GEOGEAPÏÏY 



A Transition Form. — Macroscopic. — Oue spedmeu is of a difFereut type, uot so fine 

 grained, and banded with greenish and brownish layers cut through by a A^ery perfect 

 cleavage. 



Microscopic. — Little or no carbon or other amorphous substance can be seen, but many 

 small grains of quartz of clastic origin and containing cavities with libellules. A little 

 plagioclase is observed, badly weathered, and some muscovite. Yellowish, and also pale 

 greenish substances, which are plentiful, may be considered varieties of chlorite. Scales 

 of the latter have sometimes a roughly radial arrangement about grains of quartz. The 

 brown bands contain much hydrous sesquioxide of iron. 



(2.) Region near Beaver. 



Slates. — Mtwroscopic. — A well known series of slates is found near Beaver, along the 

 railway, the rocks ranging in color from light grey to dark iron-grey, lustrous in surface, 

 sometimes almost as if polished with graphite. They have usually a well marked 

 cleavage, sometimes two, cutting at an angle of 100° to 120\ They are often finely 

 corrugated and may even show two sets of wrinklings. Some have the speckled 

 appearance of the German Knotenschiefer. Cubes of pyrite are common inclusions. 



Microscopic. — In general the components of the slates are the same as those of the 

 Spillimichene, carbon particles and perhaps other amorphous material of clastic origin, 

 with quartz in small quantities, much of a chloritic substance and numberless fibres of 

 rutile. In addition a little muscovite and also biotite with brown oxide of iron. In some 

 specimens, hoM'ever, the quartz increases greatly in quantity, and calcite also plays an 

 important part. The Knoten or Garbeu in the spotted slates are nearly opaque, so that 

 their composition could not be determined. They are perhaps of a concretionary nature. 



EocKS Intermediate between Slates and Quartzites. — Macroscopic. — A few light 

 greenish rocks from Beaver seem related to slates and quartzites, but with a leaning 

 toward mica schist. One specimen contains blebs of quartz and felspar, as though a 

 metamorphosed conglomerate with small ovoid pebbles. 



Microscopic. — The allogenous portions are much more important in size and amount 

 than in the slates. Fragments and blebs of quartz, containing fluid cavities with bubbles, 

 form much of the rock ; and greatly weathered felspar is also found. The autogenous 

 elements form larger and far more distinct individuals than in the slate. The quartz 

 fragments are often surrounded in a roughly radial way by confused scales of colorless 

 or blue-green chlorite. Mingled with it are secondary quartz, a few lamellœ of muscovite 

 and biotite, and grains of magnetite, sometimes rectangular in cross section. 



The finer grained varieties remind one somewhat of the last specimens described 

 from the Spillimichene. 



(3.) Surprise Rapid. 



Mica Schist (Sericite Schist). — Macroscopic. — Most of the rocks exposed near the 

 rapids are very fine-grained, greenish grey and with pearly, lustrous cleavage surface. 

 The schistose structure seems to correspond to the bedding. Small garnets and oblong 

 portions of dark biotite are abundant. 



