ESSENTIAL UNITY OF GNEISSES AND SCHISTS. 37 I 



It seems to me that the facts here cited, with a great multitude of others 

 of similar tenor, render it necessary to unite thegueissoid and schistoid rocks 

 under one petrographic mode of derivation. They are so inseparable on 

 any fundamental grouuds and are so blended together, both structurally and 

 mineralogically, that no reasons appear to exist for a reference of one class 

 to a mode of orip-iu fundamentally different from the mode of origin of the 

 other class. On this question, however, I only propose at present to cite 

 some observed facts. The interpretation of them may be subsequently under- 

 taken. 



Areas of Semi-Crystalline Schists.* 



The crystalline schists are succeded by a system of semi-crystalline schists. 

 They range, however, from fragmental crystalline to earthy. They succeed 

 in perfect structural conformity with the older schists, with only slight 

 indications of stratigraphic disturbance. Their attitude is generally verti- 

 cal or steeply inclined. Their position is between and surrounding the 

 gneissoid areas. In northeastern Minnesota their position is between the elon- 

 gated Basswood Area on the north and the elongated White Iron Area on 

 the south. The belt, therefore, holds a persistent strike for seventy miles. 

 In this region it is not revealed as an encircling belt, because the southern 

 half of the White Iron Area is covered by gabbro and the northern border 

 of the Basswood Area remains uninvestigated; but theSaganaga Area is 

 bordered on the northwest, west, and south by these schists, and the belt 

 passing on the south side has been traced along the north side of Gunflint 

 aud North lakes and has been identified as far east as South Fowl lake, in 

 the third range of townships east of the Minnesota meridian, twelve miles 

 west of Graud Portage. In the Vermilion Granitoid Area, however, the 

 strike of the semi-crystalline schists is circumferential. On all the sides the 

 dip is steep and it diminishes from all directions toward the centre. This 

 is the arrangement of these schists around the borders of the numerous 

 granitoid areas occurring in the region of Rainy lake and Lake of the 

 Woods. 



In each of the intervals between neighboring granitoid areas the semi- 

 crystalline schists present the structure of a simple synclinal fold. This is 

 close-pressed along the axis, and the strata are accordingly vertical. Pro- 

 ceeding toward the centre of the granitoid area, the dip in the majority of 

 cases being always toward the synclinal, becomes less steep. The granitoid 



* These, with the crystalline schists included, were named " Keewatin series " by Dr. A. C. Law - 

 son in his report of 1886, pp. 10-15. Subsequently he separated the crystalline schists under the 

 name " Coutchiching series'' (.1//.. r. Jour. Sei., 3d Ser., vol. 32. 18S0, p. 477.) The name Keewatin 

 has been employed by the Minnesota Survey in the sense thus restricted, but the term " Vermilion 

 series " was already in vogue before Dr. Lawson's separation of the crystalline schists. As the 

 spelling of Chippewa names can scarcely be regarded as fixed by any literary or scientific authority, 

 unless it be the usage of ethnographers, I suggest that the useless second "e " be dropped from the 

 name employed by Lawson. thus making it " Keuatin " (pronounced Ke- way-tin). An orthography 

 better supported by linguistic ethnology would be Ki-we-tin. 



