MICHIGAN AND WISCONSIN. 493 



Mr. T. B. Brooks ; consequently numerous statements are put forth by 

 liim as original, when in fact they had been previously published l)y 

 others. Had Dr. Rominger been more conversant with the literature 

 of the district, many errors into which he has fallen would have been 

 spared him, since he is essentially a paUeontologist. However, he ap- 

 pears to have worked conscientiously, and to have endeavored to ascer- 

 tain the truth so far as he could. 



Eegarding the so-called Laurentian granites, Dr. Rominger states : — 



" According to iny owti observations the granites of Marquette are eruptive 

 masses which came to the surface after the Huronian beds were already formed, 

 and by their eruption caused, not only the great dislocations of the Huronian 

 formation, but the half molten plastic granite masses induced by their contact 

 with the Huronian rock-beds, also their alteration into a more or less perfect 

 crj'stalline condition, and commingled with them so as to make it an embar- 

 rassing task to find a line of demarcation between the intrusi\e and the in- 

 truded rock-masses." (I. c, p. 6.) 



He also points to the fact that lamination is no proof of stratification, 

 stating that he had " in several instances seen narrow intrusive granitic 

 dyke-masses similarly laminated by the parallel arrangement of the" 

 mica scales in them." (I. c, p. 16.) 



Dr. Rominger further proceeds : — 



" The granites, considered in their present surface position, are, in relation 

 to the stratified sedimentary rocks of the Huronian series, actually the younger 

 rock, so far as the intrusion of very large masses of granite between the strati- 

 fied sediments can be demonstrated by clearly observable facts, and as the 

 other larger bodies of granite inclosing them [the so-called Huronian schists] 

 from two sides are in direct continuity with the vein granites, and lithologi- 

 cally identical with them." {I. c, p. 22.) 



While Dr. Rominger regarded part of the basic rocks as truly erup- 

 tive in the form of dikes and lava flows, he recognized also the intinisive 

 nature of much of the remainder ; but being unable, from lack of litho- 

 logical training, to distinguish between the older eruptives and their 

 associated schistose rocks, he — like Mr. Brooks — confounded them to- 

 gether, and adopted for explanation the following theory, difficult of 

 comprehension, and certainly not at all consonant with the facts ob- 

 served in the district, the difficulty lying with the observers, and not 

 with the rocks : — 



"From such a standpoint, the various crystalline hornblende rocks found in 

 association with the granites could be considered as remelted, completely 

 metamorphosed, Huronian sediments, on account of their nearest proximity to 



