208 The American Geoluyist. October, 1S95 
(h). Great nou-conforniity on the (//). Unconformity on the Green 
Archean. The rocks of (g) are Mountain gneiss and on an older 
sometimes folded with the Archean series in the Adirondacks. as late- 
so as to cause them to be con- ly announced afresh by Kemp, 
founded. 
(/). Oldest known series of crys- (/). An older series of crystal- 
talline rocks. Archean. lines. 
Litholngical Constants. 
Much has been said in late years against the evidence of 
lithologic similarity as a guide to the parallelism of rock out- 
crops in different localities ; but when it is remembered that 
in the earlier epochs of geological history great uniformity of 
oceanic and physical conditions spread over vast expanses of 
the earth's surface, and that dilferentiation of no kind had ad- 
vanced very far, it is perhaps more reasonable, in the case of 
the epochs which we are considering, to expect a uniformity 
of rocky structure over large areas than a coteniporarj^ diver- 
sity. Physical effects, as they are manifested in the ocean's 
"drama of sedimentation, Avere not modified b}^ great variations 
of depth, nor by continental shores. It was only when the 
heaving of the thin crust, perhaps under changing astronomic 
influences, finally broke it and allowed the molten interior to 
escape to the surface, that the repose of eons was disturbed 
and the sedimentary succession was varied. In the light of 
the facts which are brought together above, making a litho- 
logical and structural comparison between the eastern portions 
of New York and the Lake Superior basin, in Taconic time, it 
is at least not unreasonable to question the wisdom of the 
common practice of casting out as unreliable all evidence de- 
rivable at this horizon, from a comparison of lithological 
characters. In order to make this plainer it will be well to 
emphasize the constant lithological features that are known to 
have prevailed, simultaneously, in the two regions. 
To do this but little more is necessary, at the first glance, 
than to refer to the sequence as already stated in the fore- 
going tables. There are, however, some remarkable rock spe- 
cies, unlike any found in any other part of North America, 
either in earlier or later geological history which occur coin- 
cidently at these distant points. First of all the great anor- 
thosyte series stands prominent. This remarkable group 
under the names Norian. Upper Laurentian and Hypersthene 
