224 The American Geologist. April, i890 
group proper by a fault not yet fully ascertained."'' In sub- 
sequent examinations of the region by Logan and Hall con- 
jointly a narrow belt of Loraine shales was traced along the 
east side of the Hudson to a point a little above Hyde Park 
where the boundary between the two formations crosses to the 
west bank, and the rocks of the older series thence occup)^ 
both sides of the Hudson down to the Highlands. (Azoic 
Rocks, pp. 120-121.) 
In concluding the note of 1876, cited above, it was said "the 
author many years since pointed out that the fossiliferous 
Levis strata near Quebec hold in their conglomerates pebbles 
from the crystalline Huronian rocks which were described by 
Logan as altered Levis and Lauzon rocks. These crystalline 
schists were l)y Logan maintained to belong to this horizon 
because they are in some places overlaid by Sillery sandstone, 
but inasmuch as it now appears that the Sillery is really the 
lowest member of the Quebec group, it is clear that these crys- 
talline schists must belong to a more ancient series." 
It is to be noted that while the Second, or what we may call 
the Ordovician Graywacke,has for its lower member the Utica 
slate overlaid by the Loraine shale and terminated by the 
massive Oneida sandstone and conglomerate this order is re- 
versed, in the First or Cambrian Graywacke, the Upper Ta- 
conic as defined by Emmons, a massive sandstone there form- 
ing the base of the series. For the rest, the general lithologi- 
cal resemblances between the two Graywacke series are such 
that as we have seen, Emmons from the apparent stratigraphy 
of the Quebec section was at first led to refer it to the Sec- 
ond Graywacke, a determination accepted without hesitation 
by Logan, who shared in the general mistrust and disfavor 
shown to the later conclusions of Emmons until convinced at 
the end of 1860 that the contention of the latter with regard to 
the Upper Taconic was true. Meanwhile, accepting the metamor- 
phic hypothesis of Mather, which maintained the transforma- 
tion of tlie Levis and Lauzon sedimentary strata into crystal- 
line schists, the small amounts of oxyds of titanium, chrome 
and nickel, of magnesian silicate (and even the distinct por- 
tions of serpentine) found in certain beds of the Sillery divis- 
*See Geology of Wisconsin, 1862, p. 443, cited in the author's report 
on Azoic Rocks, E., Second Geological Survey of Pennsylvania, page 
118. 
