GEOLOGICAL EXPLORATIONS AN*) LITERATUEE. 75 



cised out of existence, and this often \vitli pungency and lack of a scientific 

 spii-it, or if it does not yield so easily to destructive criticisms is dismissed 

 with derision. On the otlier hand, all statements of previous authors 

 which seem in any way to support tlie view a(h'ocated are accepted with a 

 readiness which at times amounts to credulity. That very much was found 

 among the older writings which could he rejected goes without saying, 

 jjarticularly so since these older writers had not become possessed of any 

 of the modern petrographical knowledge, and, having onh' done the best 

 that the development of the science enabled them, very frequently and 

 naturally fell into serious mistakes. So generally, indeed, lias the opposi- 

 tion of writers to the view of the authors of this volume, or an occasional 

 unavoidable mistake, been seized upon for their condemnation that nearlv 

 all geologists who had previously written upon tlie ])re-Cambrian forma- 

 tions, save the authors themselves, are in(;luded in tlie general censure. A 

 satisfactor}' critical review of all that has heretofore been published on the 

 Archean formations of America therefoi-e remains still tit be written. 

 Unfortunately, however, it does not now seem probable that such a review' 

 can be prepared at an early date, for the author must not only be unbiased 

 and ready to go where truth leads him, but, in order tliat the review may 

 have any considerable value, he must have had an unusually wide experi- 

 ence and must have the time to verify on the ground the statements of the 

 various writers.' 



The following quotations from Part i include all that has direct refer- 

 ence to the Penokee-Gogebic district (pj). 495-497): 



Passiiiji' now to the Azoic rocks of Wisconsin, we linil tliat in 1.S70 Mr. E. T. 

 Sweet pointed out a supiwscd uncoiifonuability between the Laureiitiaii and Huroniau 

 at Peiiokee gap, stating (Trans. Wis. Acad., vol. ill, lS75-'76, pp. 4i-44): 



"When the railroad cut is completed at this locality the al)solute Junction of 

 Laurentian and overlying Huronian will doubtless be exposed. There can be no 

 doubt of the uncontbrniability of these formations, apjiroaching each other as they 

 do with a persistent opitosite dip and somewhat diflereiit strike. Uncouformability 



'The .above p;iragr.apb is left e8.sentia]ly as it was written l>y the late Ur. Irving. 1 know that 

 now Dr. Watlsworth, as state geologist of Michigan, is working on the ancient roclis of lake Superior 

 in a systematic and carcfnl manner. This later work lias leil liim to modify or abandon many of liis 

 earlier views concerning them a,s well as the pre-Cambriau of other regions. — C. R. V.-vN HrsE. 



