254 GEOGNOSY OF THE APPALACHIANS. . [XIIL. 



The view of Emmons, that there exists at the western base 

 of the Green Mountains an older fossiliferous series, underlying 

 the Potsdam, met with general opposition from American ge- 

 ologists. In May, 1844, H. D. Rogers, in his address as presi- 

 dent, before the American Association of Geologists, then met 

 at Washington, criticised this view at length, and referred to a 

 section from Stockbridge, Massachusetts, to the Hudson River, 

 made by W. B. Rogers and himself, and by them laid before 

 the American Philosophical Society in January, 1841. They 

 then maintained that the quartz-rock of the Hoosic range was 

 Potsdam, the Berkshire marble identical with the blue lime- 

 stone of the Hudson valley, and the associated micaceous and 

 talcose schists altered strata of the age of the slates at the 

 base of the Appalachian system ; that is to say, primal in the 

 nomenclature of the Pennsylvania survey. 



In 1843 Mather had asserted the Champlain age of the same 

 crystalline rocks, and claimed that the whole of the division 

 was there represented, including the Potsdam, the Hudson 

 River group, and the intermediate limestones.* The conclu- 

 sion of Mather was cited with approbation by Rogers, who 

 apparently adopted it, and declared that Hitchcock held a simi- 

 lar view. It will be seen that these geologists thus united in 

 one group the schists of the Hoosic range (regarded by Em- 

 mons as primary) with those of the Taconic range, and referred 

 both to the age of the Champlain division, the whole of which 

 was supposed to be included in the group. 



In the same address Professor Rogers raised a very important 

 question. Having referred to the Potsdam sandstone, which 

 on Lake Champlain forms the base of the paleozoic system, he 

 inquires, " Is this formation, then, the lowest limit of our Ap- 

 palachian masses generally, or is the system expanded down- 

 ward in other districts by the introduction beneath it of other 

 conformable sedimentary rocks "? " He then proceeded to state 

 that from the Susquehanna River, southwestward, a more com- 

 plex series appears at the base of the lower limestone than to 

 the north of the Schuylkill, and in some parts of the Blue 



Geology of the Southern District of New York, p. 438. 



