82 The Taconic — Marcou. 
the hydromica shale between the quartzyte and hmestone, or No 
2, or by a combination of two or more of the these parts" \^Loc. 
cit. p. 241 ]. It is difficult to imagine something more confused, 
and more difficult to be "intelligently understood" and so far 
from "an accurate definition." 
The Potsdam sandstone is wanted there, for without it all the 
structure of his classification cannot stand, and Mr. Walcott 
must have it, even if he is obliged to have recourse to "subse- 
quent faulting of the strata," to replace it in "its usual position^. 
between the Georgia and the Calciferous formations." By 
usual fositio7i Mr. Walcott means only the position which he 
has chosen to give theoretically, without a single proof to sus- 
tain it. 
c. The Stockbridge limestones and other belts and lenticular 
masses of marble inclosed in slates in the Taconic area, must be 
Calciferous-Chazy-Trenton limestone, notwithstanding the stra- 
tigraphy, the lithology and even an abnormal and special palae- 
ontology, for only a dozen of fossils of the second fauna, lost 
among the two hundred and fifty or the three hundred species 
of the supra-primordial fauna, cannot carry to Trenton Falls, 
Chazy village and Montmoi-ency falls, the three thousand feet 
of strata of the Phillipsburgh and Pointe L(Jvis group. 
D. The roofing slates and "Black slates" of Emmons, must 
belong to the Hudson-Utica group, because four graptolites re- 
quire it, according to an erroneous interpretation of the unique 
locality of Dudley observatory, and the no less erroneous deter- 
mination made by Mr. Hall of one graptolite against the good 
description and figure of Dr. Emmons. 
Without those four points [A. B. C. D.],or even if only one 
of them is proved untenable, all the classification given with 
such assurance by Mr. Walcott cannot be accepted; and I think 
I have given in the preceding pages enough reasons to reject 
them all. » 
Varia. — A few more remarks before concluding. Mr. Wal- 
cott's group No. 6, composed of red, black and green slates 
"faulted between the two parts of No. 5," containing grapto- 
lites [no names are given] is referred to his Hudson group. 
"Its distribution and relation to the other groups is shown on 
the map and in the section." On the map there is no trace of 
