White limestones of Sussex Co., JV. J. — Nason. 247 
without going into the details of the matter which an exhaustive 
and decisive treatment of the subject demands. 
This is not written in a spirit of hypercriticism but simply to 
account for the later adopting of the views advocated by Vanuxeni 
and Keating, though the subsequent adoption of their views was 
based on errors as great as these geologists made. 
While Prof. Rogers was engaged in his work in New Jersey, 
Profs. Mather, Beck, and Emmons were engaged in a field in New 
York, very similar to the highland belt of New Jersey, described 
by Prof. Rogers. This is especially true of the field occupied by 
Prof. Mather. As is very well known, the crystalline region of 
southern New York is but an extension of the same belt from 
New Jersey. 
In the report of Prof. Mather, "Geology of New York, "part I, 
vol. iv, it is a little difficult to understand just what he means 
by a primary limestone, in which he very evidently believes, for in 
a foot-note, p. 464 of this report, he sa} r s : ' < The true primary 
limestone here alluded to is the same that forms the second class 
of metamorphic limestones in this volume, and which is next to 
be described as the metamorphic limestones of the Highlands and 
west of the Hudson and of Washington count}-. " 
The last paragraph of this same page, summing up the facts of 
the I division of metamorphic rock, reads as follows : 
"After reviewing all the facts observed both by others and by 
myself, I have been led to the conclusion, that the limestones that 
are frequently crystalline, white and variegated marbles in the 
western part of Vermont, Mass. and Conn., and in the eastern 
part of New York, from mount Washington to the cit} r of New 
York (that have been described in this chapter) are Metamorphic 
Rocks — that they were originally the Mohawk limestones and Cal- 
ciferous sandstones, and that the associated rocks were originally 
tin Potsdam sandstone and the slate rocks of the Hudson valley; 
that they were in fact the rocks of the Cham/plain division, but 
much more altered and modified by metamorphic agency than the 
Taconic Rocks" I The italics and capitals arc Prof. Mather's. 
On page 4G5 he describes the second class of metamorphic rocks 
(true primary ?) under the heading ■• 11 Metamorphic Rocks of the 
Highlands, and of Saratoga and "Washington counties." 
He spent about two weeks in 1S28 and 1838 in the study <>f the 
white limestones in Orange county, New York, but having been 
