OPINIONS OF GEOLOGISTS. 47 



and in Vermont and Massachusetts, through a scries of years, have led me to the conclu- 

 sion thai they arc mctamorphic, and of the age of the Champlain division ; that they aro 

 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 mefa- 



BaOrphic." 



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) , " 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 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 the other hand, but well known lower Appalachian 

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

 Taconie 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 

 6uch 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 gncissoid 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 Taconie 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 



