1880.] A481 [Crosby. 
upon mineralogical, lithological, and stratigraphical characteristics. 
It is not my purpose here to discuss the much debated question of the 
adequacy of this class of data for the purpose named; but I may re- 
mark in passing that, in the opinion of a large and increasing number 
‘of geologists, experience has justified its use. Mistakes have been 
and are likely to be made, and yet that substantial and enduring re- 
sults have been reached few will deny. 
Stated in their most probable order of sequence, the divisions 
which have been established among the Eozoic rocks of eastern 
North America, chiefly through the labors of the Geological Survey 
of Canada, and especially of Dr. T. Sterry Hunt, are the following : 
Laurentian, Norian, Huronian, Montalban and Taconian. Of these 
divisions, the two first proposed — Laurentian and Huronian — are 
now almost universally accepted, and may be found in nearly all the 
modern manuals and text books of geology. Among the series out- 
lined more recently, the Norian, on account of its lithological sim- 
plicity, is, perhaps, the most easily recognized and the most gener- 
ally adopted; though it should be stated that some geologists of large 
experience with the rocks of this group regard them as belonging 
mainly if not entirely to the eruptive series, and therefore as insus- 
ceptible of chronological classification in the same sense as the rocks 
of the sedimentary series. The Montalban or White Mountain se- 
ries exceeds all the other crystalline formations in its lithological 
and mineralogical diversity. Itis the predominant crystalline series 
of the Appalachian region at nearly all points from Newfoundland to 
Georgia, and is now accepted as a distinct formation by many geolo- 
gists. 
The Taconian system attracts considerable attention at the present 
time ; but, although the weight of opinion appears to be against this — 
much disputed series, I am strongly convinced that it is a verity. 
Certainly those who admit the Eozoic age of the distinctly crystal- 
line gneisses and schists cannot consistently doubt the existence of 
sediments intermediate in character and position between these and 
the uncrystalline Paleozoic beds. The essentially uncrystalline con- 
dition of the lowest Paleozoic strata, even in regions of great dis- 
turbance, is well illustrated by the Acadian group of eastern Massa- 
chusetts. This group, which lies at the very base of the Paleozoic 
column, and beneath everything in the New York system, includes, 
in ascending order, the conglomerate and slate of the Boston basin ; 
and probably these are among the most highly disturbed Paleozoic 
PROCEEDINGS B.8.N. H.—VOL XX. 3l JULY, 1881. 
