698 Notes on Ciassification and Nomenclature. [Aug 
Petersburg, constituting the mountains of Grafton, and extend 
ing as a general rock to Troy, where it is succeeded by a stratum 
of argillaceous slate, which extends to the banks of the Hudson 
In a general way this group of rocks is referred to as the 
“metamorphic series,” or “transition series,” as well as tke rocks 
of the Taconic range, by other geologists up to 1842. As ager 
logical designation it had no more force than the terms used by 
Sedgwick when he referred to the rocks of the Malvern Hills 
or of the Longmynd Hills, or the term that was at first used to 
express the formation of the Helderberg Mountains in New 
York. In those early days of the century geologists made 
their designations refer to mineralogical and lithological char 
acters rather than to systematic stratigraphy. Geographic des- 
ignations had not yet been introduced with the authoritative 
endorsement of Murchison. There was but imperfect knowledge 
of systematic stratigraphy ; but geographic terms were converted, 
by an easy scale of varying terminology, into geological terms 
The “ rocks of the Longmynd” became thus the Longmynd rocks. 
The rocks of the Helderberg Mountains became thus the upper 
and lower Helderberg rocks; and Mr. Emmons sagaciously 
chose to erect the rocks of the Taconic range into the Taconic 
system. | 
It is customary to date the “Taconic System” from the ya 
1842, when it was officially announced by Dr. Emmons, and it 
is just to give the term Taconic its full right as a distinct term 
in geological nomenclature only after that date, parallel witha 
similar use of the term Cambrian; but it cannot be questi pe 
that the term Taconic was a semi-geologic term for at least 
twenty years before. 7 
It may next be asked, What was the intent of the authors of 
these names? In the absence of perfectly conclusive evidenc 
as to the historic priority of one, in all respects, over the others, 
when the facts seem to have a divided and variant significance 
this may be the only way in which a just conclusion can © 
reached. It is not necessary to enter upon the citation of facts 
or quotation of authorities. The following conclusion, SO ae ; 
Mr. Barrande is concerned, will hardly be questioned. wee ; 
to elaborate a fauna, and when that was established he denomina 
the strata the primordial zone. In doing this he went no farther 
back than 1846. t 
N 
