492 THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



its origin and perpetuity in part to erroneons observations, and in part 

 to erroneous deductions from correct observations. 



Prof. N. H. Winchell, in his Report for 1881, gives a summarj' of the 

 geological opinions held regarding the copper-bearing rocks, which sum- 

 mary he appears to have made up with additions, but without ackuowl- 

 edgment, from that previously given by Dr. Wadsworth {aiite, pp. 107- 

 109), using also the more complete exposition of views presented on 

 pp. 7G-107. For an authoritative expression of Dr. Wadsworth's views 

 he does not refer to this work (pp. 1-157), which was at that time in 

 his hands, but to a brief abstract only. (Proc. Amer. Assoc. Adv. Sci., 

 1880, XXIX., pp. 429, 430.) 



In the article previously referred to (this Bulletin, pp. 1-76), it was 

 claimed by Dr. Wadsworth as the result of aii examination of the litera- 

 ture relating to the Azoic region of Michigan, together with a consider- 

 able amount of study both in the tield and in the laboratory with the 

 aid of the microscope, that, in accordance with the early published views 

 of Foster and Whitney, the granite Avas eruptive, as were the green- 

 stones (diabase, melaphyr, etc.), part of the iron ore and jaspilite, the 

 peridotite, etc. ; and that these eruptive rocks, iniited with the sedi- 

 mentary ones, made np the Azoic system ; while there was no evidence 

 existing to show that this formation could be separated into two divis- 

 ions. It was pointed out that, in the subsequent Survey of the Lake 

 Superior region by Messrs. Brooks and Pumpelly, great ignorance of the 

 simplest principles of geology and lithology had been displayed, and 

 that no confidence could be placed in the results at which they professed 

 to have arrived.* 



We now pass to the consideration of some later publications relating 

 to the Azoic rocks of Michigan. 



In 1881, the fourth volume of the Report of the Michigan Geological 

 Survey, by Dr. C. Rominger, was published. The author of this Report 

 appears to have known nothing of the work of others, excepting that of 



* It might further have been shown that, although Major Brooks professed in his 

 Report to give a history of the scientific exploration of the Iron District of Lake 

 Superior, he entirely ignored the work of Messrs. J'ostcr and Wliitney, by whom that 

 region was first geologically mapped, and the important localities of iron ore laid 

 down. It might also have been shown that the geological map of the Lake Superior 

 region published by Messrs. Brooks and Pumpelly was, to a considei'able extent, a 

 copy of that of Foster and Whitney, and that not the slightest acknowledgment was 

 made for thus incorporating into their own work tlie geology of extensive areas 

 which had never been examined witli any detail either by themselves or by their 

 assistants. 



