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mikieand Keweenawan rocks, whicli are often Kill asfavorable in nature to the occur- 

 renceofsach remains as their supposed equivalents in the east, 2 h disregards the 

 anconformitj between the A.nimikie (and Hurouian generallj and the Keweenaw 

 Series, which unconformity Suds no parallel in the eastern series, as given bj Win 

 chell. (3) li disregards the immense and far more striking and pronounced nncon 

 formity met with in the western succession between the Keweenaw Series and the 

 overlying sandstones, which break not only finds no parallel in the east, but is to be 



contrasted with the gradation of the Nm Yotk Potsdam into the overlying Calcife a 



Sandrock. (4) It parallelizes the Keweeuaw Series, which approaches a thickness of 

 50,000 feet, of which fullj 15,000 are of purely detrital matter, with a sandstone only a 

 few hundred feet thick. 



The lithological evidence advanced is hardlj worth discussion, because of the well- 

 recognized untrustworthiness of such evidence when applied to the comparison of rock 

 formations at long distances apart. Winchell's assertions, however, of a lithological 

 correspondence between the New York Potsdam and the Keweenaw Series will not 

 bear examination. In his own words, the New York formation "is a red or graj loose 

 sandstone, often tilted or faulted, also metamorphosed, and then having the name of 

 quartzite." We look in vain in it for the greal beds of porphyrj conglomerate, the 

 immense thicknesses of basic and acid eruptive rocks, and the black shales of the Ke- 

 weenaw Series. Even the sandstones of the two formations do not approach each 

 other in character, those of the typical Potsdam being described as distinctly quart 

 whereas those of the Keweenaw Series are only very subonli ately so, being composed 



almost wholly of fragments of the feldspars or felsitic matrix of the acid eruptivee of 



the same series. The occurrence in the Keweenaw Series of beds of metamorphic 

 origin, including "gneiss, syenite, and hard, red quartzites," as stated by Winchell, I do 

 not admit. Gneiss is never met with. Peculiar red rocks, to which the name of sye 

 nite may be applied, are met with in the series, but are plainly of an intrusive nature. 

 Kocks to which the name quartzite could be applied 1 have never seen; certainly they 

 must be very rare, if they occur at all. Portions of sandstone beds locally indurated 

 by a quartz infiltration I have occasionally seen, but such rare and unimportant occur- 

 rences would hardly warrant the mention of quartzite as a characteristic of the forma- 

 tion. On the other hand, there is a distinct similarity between the typical Potsdam as 

 described and the so-called Potsdam of Central Wisconsin, where a quartzose compo- 

 sition, with local indurations due to quartz infiltration, and local developments of red 

 saudstone, often of considerable thickness, are prominent features. 



The paleontological evidence advanced by Winchell consists in the occurrence, in 

 the (Jalciferous Sandrock of New York, and in its extension into Canada, of a fauna 



nearly allied to that of the lowest fossiliferous sandst ■ of the Mississippi Valley. 



Accepting the statement as to this similarity so far as it goes, I have to say. 1 1 | that the 

 evidence is too meager to establish a complete equivalency between the Calciferous 

 Sandrock and the Mississippi Potsdam ; (2) that even if it werenotso, it would remain 

 to show that the Potsdam itself is not merely a downward continuation of the Calcifer- 

 ous, the few fossils that occur in it being insufficient to disprove this relation, while the 

 grada'iou of the Potsdam into the overlying Calciferous is a distinct indication of such 

 a relation. 



In conclusion, then, I have to say that it seems to me quite plain that the horizon 



