2272 DR. THOMAS STERRY HUNT ON THE 
upon the Pulaski shales, is seen in Herkimer county, overlying directly the Frankfort 
slates and sandstones. The same conditions, according to Horton, (Mather’s assistant in 
the Southern district of New York) occur in Orange county, where the sandstone of Sha- 
wangunk Mountain is said to rest unconformably upon the edges of the Argillite and 
Gray wacke series. 
§ 15. The following table (page 224) will show the relations of the various groups of 
strata already noticed, by a comparison of the divisions established by Eaton with those 
adopted by the New York geologists and by others. It should here be repeated that Eaton 
insisted upon the fact that the Argillite is unconformably overlaid by the First Graywacke. 
He wrote, “ while European geologists, have described a change of direction at the meeting 
of the Lower and Upper Secondary, in which the latter rests unconformably upon the 
inclined edges of the former, in North America this change takes place at the meeting of 
the Argillite and the First Graywacke.” He was careful to distinguish between the bed- 
ding and the slaty cleavage of the Argillite, the plates of which, he tells us, “ form a large 
angle with the general direction of the rock.” His diagrams moreover show both the non- 
conformity of stratification between the two, and the independent slaty cleavage of the 
lower series.* 
Eaton did not distinguish the Potsdam sandstone on the west shore of Lake Cham- 
plain from what he called the Calciferous Sand-rock, there underlying the Metalliferous 
Lime-rock—a term (borrowed from Bakewell) by which he designated the Trenton lime- 
stone with its sub-divisions, including what he called the Birdseye or encrinal marble, 
and the underlying Chazy. The Calciferous Sand-rock he described and figured as in part 
marked by geodes, (a very distinctive character), and represented it as the equivalent of the 
somewhat dissimilar Sparry Lime-rock found, to the eastward, at the summit of the First 
Graywacke. Of this Sparry Lime-rock, he both designated and figured two varieties, 
which he called veiny and tessellated. The correctness of these, and of other descriptions by 
Eaton, will be acknowledged by those who examine carefully the rocks which he described. 
§ 16. In the Lower Secondary of Eaton, what he named the Corniferous or Cherty 
Lime-rock, with its beds of chert (called by him stratified horn-rock), is the Upper Helderberg 
of later geologists, and his Geodiferous Lime-rock is as clearly the Niagara; the Lower 
Helderberg limestone, and the succeeding Oriskany sandstone, now regarded as the basal 
member of the Devonian, not being then recognized. Besides the regular division of each 
group into triads of argillaceous, silicious and calcareous rocks, which he regarded as normal, 
Eaton admitted the existence of what he called subordinate or interposed strata. To this 
class of abnormal rocks, he referred, in the Lower Secondary, the Onondaga group, with its 
marls, salt and gypsum, and also the hydraulic limestone or Water-lime above it; all of 
which may be regarded as interpolated between the Niagara and the Helderberg lime- 
stones. In the same subordinate class also were included by him the red beds of the 
Medina and the iron-ores of the Clinton. 
§ 17. It will be remembered that the Potsdam of Emmons, which (like the Calci- 
ferous Sand-rock) is often wanting at the base of the Champlain division, was unknown 
to Eaton, and hence does not appear in the table below, from which what he regarded as 
subordinate strata are also omitted. The Calciferous Sand-rock of Eaton and the underlying 


* Geological Textbook, pp. 63, 72, 74. 

