THE LOWER HURONIAN. 281 



beds in different parts of the folds. Thus on the hmbs of the folds it is 

 essentially parallel with '..!ie bedding, whereas at the ends of the folds it 

 cuts across the bedding nearly at a right angle to it. No places were seen 

 which appeared to promise a supply of good roofing slate. The rocks are 

 very generally much broken up by minor joints, but at considerable depth 

 possibly rocks might be found in such condition that roofing squares could 

 be obtained. 



These slates are everywhere intersected by numerous quartz veins, 

 especially south of Pike River Bay. The jjresence of these quartz veins in 

 the slates gave rise to the rumor of the occurrence of gold, and the early 

 history of the Vermilion district is the history of attempts to obtain gold 

 from veins in these sediments — as, for instance, at Gold Island, near the 

 northern part of the lake. 



RELATIONS OF OGISHKE CONGLOMERATE AND KNIFE LAKE SLATE. 



The relations of the rocks to one another are so clearly shown at so 

 many places that it is scarcely worth while to discuss them. There is a 

 great conglomerate normally overlain by and grading up into a great 

 thickness of slate through the intermediate graywackes. In the con- 

 glomerates occur masses of slate, and in the slate likewise occur masses of 

 conglomerate. Evidently the series is a geologic unit which is divisible into 

 two parts, the conglomerates and slates, only by an arbitrary line below 

 which the conglomerate predominates on the whole, and above which the 

 slates predominate. In an article on the Vermilion area Smyth and 

 Finlay" described the slates as the oldest rocks of the area, instead of 

 nearly the youngest. 



RELATIONS TO ADJACENT FORMATIONS. 



Relations to Archean. — Where the series is in contact with the Ely 

 greenstone and the Soudan formation, the conglomerate normally lies next 

 to these rocks, and consists to a great extent of pebbles derived from them. 

 Hence, having been derived from them, it must overlie them stratigraphic- 

 ally and is therefore younger than they. 



Occasionally the conglomerate occurs in very thin belts, too narrow to 



«The geological structure of the western part of the Vermilion range, Minnesota, by H. L. Smyth 

 and J Ralph Finlay: Trans. Am. Inst. Min. Eng., Vol. XXV, 1895, p. 602. 



