v< 



-t 

 ^ 



82 



BULLETIN OF THE 



marked : " There can be no doubt, however, that the metals found in 

 the Lake Superior amygdaloidal trap, have been fused at as high a 

 temperature as was required to liquify the rocks in which they are 

 found, for they bear evident marks of entire fusion, and are as vesicular 

 as the common lavas of Vesuvius, Etna, and Peak of Teneritfe." * In 

 one of the later paperst he states : " It is obvious, both from the crys- 

 talline forms and the mode of occurrence of this copper, that it was 

 deposited from a state of igneous fluidity ; and, from the circumstance 

 that the walls of the vein are encrusted with Launionitc, it would 

 appear that the spar vein itself is of igneous origin. Many other in- 

 stances of a similar kind indicate that the calcareous spar veins, which 

 traverse the conglomerate ^nd sandstone rocks, are true veins of igneous 



i 



7. 



■2, 



S 



y 



origm. 



Mr. Bela Hubbard J regarded the sandstones on both sides of Kewee- 

 naw Point as Potsdam in age, and held that the traps were eruptive in 

 it. He regarded, however, the conglomerate and the "mixed conglom- 



erate and sand rock " lying to the northwest of the Point as of later 

 origin than the trap and composed of itadebris. Concerning the *' mixed 

 conglomerate and sandrock" he states: "As the finer strata of this 

 rock have been mistaken by some for the red sandrock, hereafter de- 

 scribed, it is important to observe that a very marked difference exists 

 between the two rocks; for, while the latter is made up of materials 

 derived from the several rock formations of the country, and into which 

 quartzose grains enter most largely, the former is wholly derived from 

 the trap rocks." The "red sandrock*' is said to be in nearly horizon- 

 tal strata, but having on the coast a slight dip inland, which becomes 

 "more apparent as it approaches the bayin of Portage Lake. In its 

 approach to the trap, however, it is found more or less tilted from its 

 original horizontal position, and is also very much altered by its contact 

 with that igneous rock. The evidences both of the deposition of this 

 extensive formation, in calm and shallow waters, and of the subsequent 

 changes induced in it by the trap rocks, when in a fused or heated state, 

 are very apparent." 



Prof. H. D. llogersj stated that "at the Eagle River mine, and 



* See also Proceedings of same Society, U. 110-114, Mar. 4, 1846. Am. Jour. 

 Sci., (2,) IL 118, 119. 



t Proc. Best. Soc. Nat. Hist., 1846, U. 112. 



} Mineral Region of I/ike Superior, by J. Hongliton, Jr. nnd T. W. P>nstoL See 

 also Senate Documents, 1849-50, 31st Cong., 1st Sess., III. 802-842, and 1845- 

 46, 29th Cong., 1st Sess., VII., No. 357, pp, 2-29, 



§ Proc. Bost Soc. Nat. Hist., April 1, 1846, II. 124, 125. 



