Association of American Geologists and Naturalists . 151 



side of Vermont and Massachusetts, have been carefully studied by Em- 

 mons, Hitchcock and Mather, all of whom appear to have arrived at 

 different conclusions concerning them. Since the same or a very anal- 

 ogous group of strata ranges at intervals, holding the same relative po- 

 sition, 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 inspec- 

 tion 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 palseozoic fossiliferous rocks of the Cham- 

 plain and Hudson valley on the west, but holding an intermediate place 

 in the scale of time. His principal argument in defence of this view, 

 is that the order of succession of the component members of the group, 

 is essentially different from that witnessed in the sandstone, limestone 

 and slate of the Champlain division, and he denies that the theory of 

 plication of the beds, advanced originally by myself and my brother, 

 and applied to this very region, can reconcile the seeming want of agree- 

 ment. Now it is true that the apparent order of superposition in the 

 Taconic belt, is in discrepancy with the well known succession of the 

 Champlain formations, but this is precisely what should arise from the 

 introduction of those complete folds or doublings together of the strata 

 which we have conceived to exist ; and I would add that the sections 

 furnished by Prof. Emmons and Prof. Mather in their reports, if resolved 

 by the introduction of the flexures supposed by us, will all of them dis- 

 play, for their western portions at least, the normal order of superposi- 

 tion of the Champlain rocks. 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 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 overturn- 

 ing of the whole series. The plication was shown to be greater along 

 the Berkshire valley and the ridges east, the granular Berkshire marble 

 was identified with the blue limestone of the Hudson valley, but meta- 

 morphosed by heat, and the associated micaceous, talcose, and other 

 schists were referred in the language of the communication, to the slates 



