272 T. S. Huni— History of Pre-Cambrian Rocks 
as to the relations of the Laurentian and Huronian in this re- 
gion. 
The Primary age of the Highlands of southern New York, 
and their extension in what is called the South Mountain, as far 
as the Schuylkill, was now unquestioned, but the crystalline 
rocks to the east of this range, while regarded by Haton and 
by Emmons, as also forming a part of the Primary, were, by 
Mather, as we have already seen, supposed to be altered paleo- 
zoic strata. These rocks in New England, with the exception 
of the quartzites and limestones of the Taconic range, were by 
him assigned to a horizon above the Trenton limestone of the 
New York system, and portions of them were conjectured by 
other geologists, who adopted and extended the views of Mather, 
to be of Devonian age. 
The characteristic crystalline schists of New England and 
southeastern New York, passing beneath the Mesozoic of New 
Jersey, re-appear in southeastern Pennsylvania, where they were 
studied and finally described by H. D. Rogers in 1858. Ac 
cording to him these crystalline schists, while resting uncon- 
formably upon an ancient (Hypozoic) gneissic system, were 
themselves more ancient than the Scolithus-sandstone, which 
consider in detail in a future paper. In it are included the 
iron-ores of Reading, Cornwall and Dillsburg, in Pennsylvan'@ 
The views of H. D. Rogers with regard to the crystalline 
schists of the Atlantic belt were thus, in effect, if not in terms 
a return to those held by Eaton and by Emmons, but were 1? 
direct opposition to that maintained by Mather, which had bee2 
