144 DE. THOMAS STERUY HUNT ON THE 



to the paleozoic age of the Lower Taconic rocks, the view put forward by Mather, that 

 the great region of gneisses and crystalline schists with limestones, lying to the east of 

 these, consists of more highly altered paleozoic strata, had become discredited It was, as we 

 have seen, abandoned by H. D. Rogers for Pennsylvania, in 1858, and by W. B. Rogers for 

 Virginia, where he recognized in the pre-Taconian rocks the same great divisions which I 

 had elsewhere pointed out. The history of the studies of Thomas Macfarlane and my 

 own, which showed conclusively the pre-paleozoic age of the extension of the New Eng- 

 land crystalline schists into the Province of Quebec, has already been told elsewhere.-' 



§ 184. It was, therefore, with some surprise that geological students found J. D. Dana, 

 in 1880, attempting to resuscitate, in its completeness, the discarded view of Mather. In 

 an elaborate paper on "The Geological Relations of the Limestone Belts of Westchester 

 County, New York," which appeared that year, Dana, following up the reasoning already 

 noticed (§ 161), by which he sought to siistain the paleozoic age of the Lower Taconic 

 rocks, proceeds to assume that the crystalline marbles enclosed in the gneisses, as well as 

 the gneisses and crystalline schists of the region named, are altered rocks of paleozoic 

 age. To quote his conckisions : "The limestone of Westche.ster County and of New York 

 Islaud, and the conformably associated metamorphic rocks, are of Lower Silurian age," 

 and, farther, " the limestone and the conformably associated rocks of the Green Mountain 

 region, from Vermont to New York Island, are of Lower Silurian age."^^ His argument 

 in favor of these assumptions, appears to be briefly this : that the crystalline limestones of 

 the gueissic series, the granular Lower Taconic marbles, and the fossiliferous Cambrian 

 and Ordovician limestones found among the uncrystalline sediments of the Appalachian 

 A'allev, along the western flank of the crystalline belt north of the Highlands, are but 

 three different conditions of one and the same calcareous series, and, hence, that the gi'eat 

 area of crystalline rocks south of the narrow range of the Highlands (of which he admits 

 the eozoic age) consists of paleozoic strata, Cambrian or Ordovician in age. 



§ 185. Dana, having announced his conclusions as above, adds.: "The e^àdence which 

 has been adduced, though then but partly discerned, led Professors W. B. and H. D. Rogers, 

 and Professor W. W. Mather, nearly to the results here reached." In support of this asser- 

 sertion, he refers to Mather's report of 1843, in which, as we have seen, the hypothesis was 

 advanced, and also, under the head of " Professors Rogers," to a paper by them in 1841, ia 

 the Proceedings of the American Philosophical Society, as well as to a statement in the 

 American Journal of Science for 18*72 (Vol. IV, page 363). This, the reader will find to be 

 nothing more than Dana's assertion that the Messrs. Rogers, in that same paper of 1841, 

 maintained the Champlain age of the Lower Taconic series, — a view which, as we all are 

 aware, one of them, some years later, abandoned for that of its Devonian age. These 

 eminent geologists did, for a time, put forward the view (afterM^ards relinquished) that 

 the gneissic series of the White Mountains consists of altered Silurian (Oneida-Clinton 

 strata), and Mather, in his argument, made the most of the error of H. D. Rogers, who 

 mistook, in 1840, certain interstratified crystalline limestones among the Primary gneisses 

 of New Jersey for superincumbent limestones in an altered condition, but Dana fails to 

 show that the Messrs. Rogers ever maintained the paleozoic age of the great series of 



=' Hunt, Azoic Rocks, pp. 182-188, and Amer. Jour. Science, 1880, xix, 272-275. 

 -" Amer. Jour. Science, 1880, xs, 455. 



