472 ADDRESS OF T. STERRY HUNT. 
that the absence of all but the highest beds of the Levis along the 
eastern limit of the Potsdam, near Swanton, Vermont, while the — 
whole thickness of them appears a little farther westward, makes 
it probable that there is a want of conformity between the two; 
and I have in this connection insisted upon the entire absence in 
this locality of the Calciferous, which is met with a little farther 
south in the section just mentioned, as another evidence. of the 
same unconformity.* There are also, I think, reasons for sus- 
pecting another stratigraphical break at the summit of the Quebec 
group, in which case many problems in the geological structure of 
this region will be much simplified. 
It should be remembered that the conditions of deposition in 
some areas have been such that accumulations of strata, corres- 
ponding to long geologic periods, and elsewhere marked by strati- 
graphical breaks, are arranged in conformable superposition ; and 
moreover that movements of elevation and depression have even 
caused great paleontological breaks, which over considerable areas 
are not marked by any apparent discordance. Thus the remarka- 
ble break in the fauna between the Calciferous and the Chazy is not 
accompanied by any noticeable discordance in the Ottawa basin, 
and in Nebraska, according to Hayden, the Potsdam, Carbonifer- 
ous, Jurassic and Cretaceous formations are all represented in 
about 1200 feet of conformable strata.; In Sweden the whole 
series from the base of the Cambrian to the summit of the Upper 
Silurian appears as a conformable sequence, while in North Wales, 
although there is no apparent discordance from the base of the 
Cambrian to the summit of the Lingula flags, stratigraphical 
‘breaks, according to Ramsay, probably occur both at the base and 
the summit of the Tremadoc slates, { which are considered equiva- 
lent to the Levis formation. 
We have seen that, according to Logan, a dislocation 4 little bac 
the north of Lake Champlain causes the Quebec group to overlie 
the higher members of the Champlain division. The same uplift, 
according to him, brings up, farther south, the Red sandrock of 
Vermont, which to the west of the dislocation rests upon the up- 
turned and inverted strata of various formations from the Calcif 
erous sandrock to the Utica and Hudson River shales. These 
* Amer. Jour. Sci., II, xlvi, 225. 
t Ibid., II, xxv, 440. 
+ Quar. Geol. Journal, xix, page xxxvi. 
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