1 7^ ■j'''^- ^ ■ Winche'u on a greet 'Pj'imordLii. Quartzyte. 
What do we have then? — a great primordial ({iiartzyte, 
which under different names extends from New England, 
through Canada, into Wisconsin, Minnesota and to the Black 
Hills of Dakota. It has also been identified further west, mak- 
ing it in American geology truly a continental formation, 
Avhose simple, persistent and uniform characters not only ren- 
der it readily recognizable but impart to it that feature \vhich 
all continental formations possess. 
Many important and interesting corollaries spring from this 
generalization. 
1. The Potsdam, as claimed 1)\- I'lofs. Hitchcock and Jules 
Marcou, is a part of the Taconic. 
2. The Huronian is the equivalent of the Taconic, at least 
so far as the common possession of this quaitzyte makes them 
identical. 
3. The IJarrahoo quartzyte, the Barron count} quartzyte, 
the Wauswaugoning quartzyte, the Sioux quartzyte and the 
Black Hills quartzyte are identical parts of the Taconic. 
4. This would leave the "black slate" of Bald moun- 
tain and the "Taconic slate" as the only portions of the 
Taconic not proven to be equivalents of some parts of the New 
York series; and if Mr. Walcott's inference that these slates are 
the deep-water equivalents of the off-shore deposits of the 
^'granular c|uartz" be correct, no part of the Taconic would 
remain as an intlcpendent formation. 
5. If, however, the succession of strata east of the Adiron- 
dack mountains is the same as in the area of the original Huro- 
nian and in northeastern ]Minnesota, this great quartzyte im- 
mediately overlies, in some places, a black slate and in others 
it lies unconformably on granite; hence the granular quartz of 
Emmons probably belongs above his black slate. 
6. The Potsdam quartzyte-sandstone should be sought for 
not only in that part of Canada where it has been represented 
as wanting, but also in northern Michigan where it has been 
•supposed to be represented by the "eastern sandstones." 
