104 



THE CAMRRTAN. 



(bull. 81. 



ami nation. He found a species of Salterella, which lie identified as 

 Salterella pulchella. He observes that the Winooski marble, both at 

 Swanton and St. Albans, seems to underlie the Georgia slates, and h( 



says : 



It is generally of a reddish, mottled color, but sometimes gray or greenish. The 

 limestone at the Straits of Belle Isle, in which S. pulchella is found, is also red, gray, 

 aud greenish ; and is, I have no doubt, of the same age. At this latter locality it 

 overlies a red or brownish sandstone, conformably, which holds Scolithux linearis. I 

 consider the Belle Isle sandstone to be the " Quartz rock " of the Green Mountains of 

 Vermont. In that case, the limestone at Belle Isle occupies, sfratigraphically, the 

 position of the Stockbridge limestone as represented by Dr. Emmons in his American 

 Geology, part 2, p. 19. ' 



Under the title "Geology of Vermont," Prof. 0. H. Hitchcock tabu- 

 lates the formations of that State. 2 The Potsdam group is made to 

 include the Ked Sand rock, part of the Hudson River slate, part of th< 

 Georgia slate, most of the quartz rock, and the Potsdam sandstone of 

 West Haven. Speaking of the latter he says, the Potsdam rocks flank 

 the gneiss upon the west side as far north as Middlebury. He further 

 observes that the quartz rock is probably the same as the red sandstone ; 

 that both are overlain by the Levis 3 limestone, and resemble each other 

 very much near their supposed union. " I find this view of the identity 

 of those two formations confirmed by the late map of the Canadian sur- 

 vey, published in 1866." 



In an article on some points in the Geology of Vermont, Dr. T. S. 

 Hunt states : 



It happens, then, from the facts already set forth, that the Potsdam formatiou, 

 which at its outcrop at the foot of the Adiroudacks and Laurentides includes only 

 from 300 to 700 feet of sandstone, is represented a few miles to the eastward by not 

 less than 2,000 feet of dolomites, sandstones, and slates, and moreover that occupy- 

 ing a position between the calciferous and chazy formations, which are contiguous 

 at their eastern outcrop, there becomes intercalated within this short distance a fos- 

 siliferous group, several thousand feet in thickness. 4 



The explanation of this is quoted from Logan's opinion, to the effect 

 that the Potsdam sandstone accumulated along the shore, while shales 

 and limestones were accumulating to a greater thickness in the deeper 

 water of the adjacent ocean. In summing up the evidence as to the 

 age of the rocks of western Vermont he says : 



All the evidence, paleontological and stratigraphical, as yet brought forwarc 

 affords no proof of the existence in Vermont of any strata (a small spur of Lauren- 

 tian excepted) lower than the Potsdam formation, which the present advocates o( 

 the Taconic system regard as forming its summit. * * * That strata still older 

 than the Potsdam of New York and Vermont were deposited in some portions of the 

 oceanic area is apparent from the existence in New Brunswick of the St. John's 

 slates holding a Primordial fauna older than the Potsdam, and it is not impossible 



»Op. cit,,p.351. 2 Am. Assoc. Proc, vol. 16, 1867, p. 120. 



3 Levis group, including the " Eoliau limestones," "Hudson .River limestones," and the greater por» 

 tion of the Georgia slate. (Op. tit., p. 120.) 

 4 On some points in the geology of Vermont. Am. Jonr. Sci., 2d ser., vol. 46, 1868, p. 225. 



