10-1 A. WINCHELL A LAST WORD WITH THE HURONIAN. 



the south. Dr. Bell stated that the train, before arriving at Vermilion river, had 

 passed over these slates for about five miles, viz., through a very flat and good agri- 

 cultural tract, indicating a profound change in the underlying rock, inasmuch as, up 

 to the place of entering on these slates, the country had been very rough, with fre- 

 quent exposures of the rock. The slate is black (or purplish black when dry), gen- 

 erally fine-grained, yet with some evident grains of quartz. * * * From the Ver- 

 milion river, traveling still southwest, we passed on to a lower series of strata, the dip 

 being to the southeast. This is a slate conglomerate, and causes an immense ridge, 

 150 feet high, more or less," 



Speaking of an apparent unconformity at Wahnapitse, which we were not 

 allowed sufficient time to examine, he says : 



" Subsequent!}' Dr. A. C. Lawson reexamined this point in order to get abetter 

 idea of the relations of the formations, and, according to verbal description from him, 

 there appears to be an unconformity of stratigraphy at Wahnapitse similar to that at 

 Penokee Gap, Wisconsin. At the immediate contact the lower rock is the fine mica- 

 ceous gneiss or mica schist, probably belonging to the series seen at North bay (Lake 

 Nipissing), and the upper rock is quartzite and gray argillite interbedded " (p. 52). 



Other evidences of two unconformable systems were found at the Stobie 

 mines (pp. 52, 53). In conclusion, he says : 



"It appears, therefore, that both northwest from Sudbury and eastward from 

 Algoma there are two formations " (p. 57). 



LITHOLOGICAL DISCORDANCES IN THE LAKE HURON DIVISION. 



We have next to direct attention briefly to the lithological contrasts noted 

 between the two divisions of the original Huronian. We will confine the 

 comparison to the two slate conglomerates. 



Murraifs and Logan's Descriptions. — We have already quoted passages 

 from Mr. Murray's report of 1848 (see arite, pp. 86, 93). From these it ap- 

 pears that Murray did not distinctly note the aspects of the slate conglom- 

 erate as chronologically successive, but the lithological distinctions were 

 very clearly and fully drawn. One is "more argillaceous," "generally 

 black," with "a very symmetrical jointed structure, dividing the rock into 

 rhombohedral forms," often "passing into a conglomerate" with pebbles 

 " imbedded in a black argillaceous matrix." The other is " gray or green," 

 " usually more or less silicious, and frequently very micaceous," sometimes 

 " almost exclusively composed of mica." " Some parts were marked by 

 small, shining specks of chlorite," and in some epidote was present. " In 

 these epidotic slates the prevalent color of the rock was gray." In his sum- 

 mary of results, however, he puts the " black argillaceous shales and con- 

 glomerates" above the separating limestone, and the micaceous and chloritic 

 slates below; so this, finally, is evidence that Murray did not fail to notice 

 not only the contrasts of the slates, but also their order of sequence. 



