OPINIONS OF GEOLOGISTS. 47 



and in Vermont and Massachusetts, tlirough a series of years, liave led me to the conclu- 

 eion tlial they are metamorphic, and of the age of the Chaniplain division ; that they aro 

 the altered limestones, slates and sandstones of that division. 



" Tiie while 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 Ijeforc the American Association of 

 Geologists and Naturalists, at Washington, in May, 1844, sets forth the same opinions : 



He proceeds (Journal of Science, p. 150) , " Let us imjuire 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 sirata, 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 Taconie 

 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 liie other hand, l)ut well known lower Appalachian 

 strata, disguised by some change of mineral type, and by igneous metamorphosis? These 

 Taconie rocks, under the form they assimie 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 tlieir age, while it has a wide bearing on any general classification of our 

 formations, ought certainly lo 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 Taconie 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 Chaniplain and Hudson valley on the west, but holding an intermediate place 

 in the scale of time. 



" This identity of the so-named Taconie system, with the formations of the Hudson and 

 Chaniplain 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 



