320 The American Geologist. NOvcmhiT, 13% 
PreUmiiiury Repoii on tlic Marqiiclic /roii-licdriiKj Dislrict of Midi - 
igon. By Charles Richauu VanHise and William Shirley Bayley. 
With a chai^ter on the liepuhlic TroiujJi, Vjv Henry Lloyd Smith. 
(Fifteenth U. S. Geol. Report, pp. 477-650. with fourteen plates and 
twelve figures in the text.) The f^eneral geological map of the district 
here described, on the scale of a mile to an inch, with contour lines for 
each 50 feet, covers an extent of thirty-eight miles from the vicinity of 
Marquette west by Negaunee and Ishpeniing to Michigamme, with a 
width of nine miles, excepting that on the south it reaches three miles 
farther in the valley of the Michigamme river to Republic. The base- 
ment complex of Arehean rocks on the north comprises the Mona 
schists, Kitchi schists, gneissoid granites. ?iornbIende-syenite. dike 
rocks, and peridotite: while on the south it is chiefly granitic, with Ihe 
Palmer gneiss and dike rocks. 
The stratified Algonkian rocks are divided in the Lower and Upper 
Marquette series, which are regarded as equivalent with the original 
Huronian north of lake Huron. The lower series includes, in ascending 
order, the Mesnard quartzite, K(ma dolomite, Wewe slate, Ajibik 
quartzite, Siamo slate, and the Negaunee formation of iron-bearing 
slates and schists, the last namid formation being about 1,000 feet 
thick. In the Upper Marquette series, following the same ascending- 
order, are the Ishpeming quartzite, the Bijiki schist, and the Michigam- 
me and Clarksburg formations. The present thickness of each of the 
two Marquette series is about 5,000 feet, or less; and they are folded and 
fractured in a very complex manner, with much metamorphism. 
Concerning the minute fracture and deformation (if these series of 
rocks, the authors remark: "A microscopical study shows that not a cu- 
bic inch of material has escaped dynamic action. Almost every original 
grain of fair size gives evidence of interior movement. The rocks have 
been kneaded throughout. While as a further consequence of dynamic 
action there has been local faulting at various places, with two or three 
exceptions no important faults have been observed in the district 
Had the rocks which are now exposed not been deeply covered, it is 
hardly possible that the complicated folding could have occurred 
without complicated faulting." 
As in the Penokee district of Wisconsin and the Vermilion iron 
range of Minnesota, the ore deposits seem to have been formed chiefly 
after the regional folding took plac3. Surface water.-^, bearing organic 
acids and percolating down through the iron-bearing rocks, received 
their iron into solution, and deposited it in the rich ore bodies where 
they encountered alkaline and silica-removing waters furnished by the 
alteration of the adjoining igneous rocks. w. r. 
The Origin and Rdatioiis of Central Marylaiifl Granitea. By 
Charles RoLLiN Keyes. With an Introduction on the General Rela 
tions of the Granitic. Rocks in the Middle Atlantic Piedmont Plateau, 
by Georgk HuNTiNnroN Williams. (Fifteenth U. S. Geol. Report, pp. 
G51 740, with 22 plates, and nine figures in the text.i In the introduc- 
