62 THE MARQUETTE IRON-BEARIXG DISTRICT. 



stratified sediments, but tliev are folded and broken in such a way that 

 their true nature was for a Ling- wliile misunderstood" (p. 758). The dis- 

 triliution of the ore l)odies is beheved to be " dependent upon the immense 

 surface erosion wliicli this region has suffered. This has removed by far 

 the greatest part of the ore that originally existed here, leaving it only 

 where it formed masses of unusual magnitude and solidit}-, which have 

 resisted the erosive action, or where, in synclinal troughs, it has been 

 bevond the reach of the glaciers, which have ground off all the more 

 elevated portions" (p. 758). 



In this view the ores are manifestly supposed to have existed as an 

 extensive bed over the Marquette Huronian area, of which tlie j)resent ore 

 bodies are the remnants. This we now know to be contrary to the facts. 

 The irregular distriliutiou of the ore bodies in the region is not the result 

 of erosion, Init is tlie result of the action of secondary processes under 

 especially favorable conditions, prevailing only here and there throughout 

 the district. 



1S7.5. 



Ptjmpelly, Raphael. On pseudomorpli.s of chlorite after garnet at the Spurr 

 Mountain iron mine, Lalie Superior. Am. Jour. Sci. (3), Vol. X, 1875, pages 17-lil. 

 With plate. 



This article is of a mineralogical nature. In it the author describes 

 the well-known chlorite pseudomorphs of garnet occurring in the chlorite- 

 scliist overlving the ore bed at the Spurr mine. The chlorite-schist is 

 composed of minute flakes and needles of chlorite, through which are 

 scattered small octahedra of magnetite and the garnet pseudomorphs. 

 From the result of his investigation of the rock the author infers that the 

 schist was originally an argillaceous limestone (,>r marl that was changed 

 by metamorpliic processes into its present form. 



Whittlesey, Charles. Physical geology of Lake Superior, rroc Am. As.s. 

 Adv. Sci., Vol. XXIV, 1875, pages GO-72. With map. 



Whittlesey den-ies the existence < "f a true Laurentian series in Michigan. 

 The granitic rocks, heretofore regarded as belonging in this series, are 

 eruptive, as shown Ijy their analyses. In some instances in the Mart^uette 



