GEOLOGICAL EXPLOEATIONS AND LITEKATURE— 1883. 97 



tlie Marquette range, thougli nowhere so stated, since nearly all of the 

 observations upon which it is based were made in the hard-ore mines. It 

 is interesting in that it recognizes the sedimentary origin of these ores and 

 ascribes their concentration to the action of moving water, an agency whose 

 geological impoi'tance in this district had hitherto been largely overlooked. 

 The large regular beds of ore formed in the district are thought to have 

 been deposited originally as beds of bog ore. 



Claassen, Euo. Mineralogical notes. Am. Jour. Sci. (3), Vol. XXIII, 1882, 

 page 07. 



In this vear also Edo Claassen published a note giving the record of 

 an analysis of orthoclase crystals found implanted on hematite in one 

 of the Cleveland mines. He also describes polyhedi'al cavities in several 

 micaceous hematites, supposed to have been produced by the removal of 

 crystals of pyrite from the midst of the ore. 



1883. 



Irving, R. D. The copper-bearing rocks of Lake Superior. Third Ann. Hept. 

 U. S. Geol. Survey for 1881-82, Washington, 1883, pages 89-188. With geological map 

 of Lake Superior region. 



The year 1883 marks the entrance of the geologists of the newly 

 organized United States Geological Survey into the discussion of the 

 Marquette problems. Prof. R. D. Ir\-ing was appointeil to take charge 

 of the work in the Lake Superior region, and from the date of his tii'st 

 report unck^r the auspices of the Survey until his death in 1888 he devoted 

 himself energetically to the solution of the problems concerning the 

 con-elation of the Lake Superior formations and those connected with the 

 geology of the iron-bearing rocks, more particularly those relating to 

 the Peuokee and to the Marquette series. It is safe to say that, consider- 

 ing the short time in which he worked, no one has added more to the 

 clear understanding of the relations existing between the various rock 

 series in the Marquette district than has Professor Irving. 



In a preliminary account of the Keweenawan series Irving discusses 

 the relations of this series to the older rock series associated with it. In 



MON XXVIII 7 



