426 THE PENOKEE IKON BEARING SERIES. 



are largely volcanic tuffs and lavas, the objection loses its force, for it is 

 well known that this class of material varies greatly in thickness within a 

 short distance. 



Tlte soufhfrn dips. — The slaty phases of the greenstone-congloinerate 

 and the clay-slates north of the greenstone-conglomerate in the W. ^ of T. 

 47 N., R. 43 W., Michigan, so far as observed, appear to dip south, at 

 least they possess a parting which dips in this direction. This apparent 

 southern dip vai-ies from 55° to 80°. But the southern dips are not 

 universal; for instance, in one exposure in the SE. ^ See. 17, T. 47 N., R. 

 43 W., Michigan, an exposure has a northern diyt, although the s ates a 

 short distance southward have the ordinary dip of the locality. Of far 

 greater importance, the jaspery rocks in the south part of Sec. 18, T. 47 

 N., R. 43 W., IMichigan, have an unmistakable northern dip. The other 

 extreniely ferruginous rocks in the northern frag-mental belts, in Sees. 13 

 and 14, T. 47 N., R. 44 W., Michigan, are too massive to furnish dips. 

 Whether the api)arent southern dips represent true bedding or cleavage it 

 seeuis impossil)le to certainly determine from the exposure or from the 

 examinations of thin section. In the cases of one or two ledges showing- 

 southern dips, an apparent bedding transverse to this parting was found, 

 but this was exceptional. 



All the rocks of the iron-bearing belt situated in the southern part of 

 the Eastern area, from the west part of Sec. 23, T. 47 N., R. 44 W., Michi- 

 gan, to the northwest part of Sec. 23, T. 47 N., R. 43 W., Michigan, have, 

 so far as observed, a northern dip. The slates prominently exposed in two 

 places in Sec. 21, T. 47 N., R. 43 W., Michigan, below the iron-bearing 

 belt, have unmistakable northern dips, as have also the half fragmental 

 slates and schists interlaminated with the rocks of the iron-bearing belt 

 just above. If we had l)ut the E. h of 'i\ 47 N., R. 44 W., Michignn, and 

 the AV. § of T. 47 N., R. 43 W., ]\Iicliigan, to deal with we would feel 

 inclined to explain tlie structure by considering the rocks as a synclinal 

 trough, in which the greenstone-conglomerate overlies the fragmental 

 rocks to the north and south of them. This would necessitate that the 

 north arm of the trough, rising into an anticlinal, had again descended, 

 di])ping to the north, antl that this part of the fold had been removed by 



