OPINIONS OF GEOLOGISTS. 
47 
and in Vermont and Massachusetts, through a series of years, have led me to the conclu¬ 
sion that they are metamorphic, and of the age of the Champlain division ; that they are 
the altered limestones, slates and sandstones of that division. 
£< The white limestone containing plumbago and various crystallized minerals, is another 
point on which there are various views. I have come to the conclusion that it is meta¬ 
morphic.” 
The following extract from Prof. Rogers’s Address before the American Association of 
Geologists and Naturalists, at Washington, in May, 1844, sets forth the same opinions: 
He proceeds (Journal of Science, p. 150), u Let us inquire how far we in the United 
States have proceeded in the same labor, of firmly establishing some of the more important 
limits between the several portions of geological time as recorded by our strata, and their 
organic remains. And first, let us examine the conclusions reached regarding the com¬ 
mencement or dawn of the whole fossiliferous period. The fixing of a base for the 
palaeozoic rocks of the United States, is a problem scarcely less difficult than that of 
determining the lower limit of the corresponding system in England, to which the admirable 
sagacity of Sedgwick has been so usefully directed. Do we possess in the so-called Taconic 
system of rocks lying to the southeast of the unequivocally fossiliferous strata at the base 
of the New-York or Appalachian system, an independent mass of formations of an unques¬ 
tionably earlier date ; or are these, on the other hand, but well known lower Appalachian 
strata, disguised by some change of mineral type, and by igneous metamorphosis? These 
Taconic rocks, under the form they assume along the eastern boundary of New-York, and 
western side of Vermont and Massachusetts, have been carefully studied by Emmons, 
Hitchcock and Mather, all of whom appear to have arrived at different conclusions con¬ 
cerning them. Since the same or a very analogous group of strata ranges at intervals, 
holding the same relative position, the whole distance from Vermont to Georgia, the 
question of their age, while it has a wide bearing on any general classification of our 
formations, ought certainly to admit, sooner or later, of settlement, when so many and 
such noble transverse sections are opened to inspection by the river gorges which cut the 
Blue ridge. 
“ Prof. Emmons considers the granular quartz, slate and limestone of the Taconic hills 
and the Stockbridge valley, as constituting a distinct group of strata, neither appertaining 
to the true gneissoid or mica schist system on the east, nor to the palaeozoic fossiliferous 
rocks of the Champlain and Hudson valley on the west, but holding an intermediate place 
in the scale of time. 
“ This identity of the so-named Taconic system, with the formations of the Hudson and 
Champlain valley, was announced by my brother and myself, in the beginning of 1841, 
to the American Philosophical Society. By the. aid of a section from Stockbridge towards 
the Hudson river, we showed the existence of numerous close anticlinal and synclinal folds, 
and thus explained the apparent inversion of the dip, which other geologists had ascribed 
to one general overturning of the whole series. The plication was shown to be greater 
