124 The Taconic Question Restated. [ Feb. 
§ 13. Meanwhile, Emmons continued his studies, and in 1844 
published his monograph on the Taconic system, which was in 1846 ` 
republished in his “ Agriculture of New York,” where it forms 
Chapter V. (pp. 45-112). Therein, while giving a more detailed 
account of the Taconic system, he made one important and sig- 
nificant change. In 1842, while maintaining that the upper por- 
tion of this is “the lower part of the Silurian system,” he had 
- nevertheless supposed that the whole succession was deposited 
before the time of the lithologically dissimilar Champlain division, 
which, although the base of the New York system, was not by 
him regarded as the base of the Silurian. In this he was at 
variance with the teachings of Eaton, who already, as early as- 
1832, had declared the Transition or Sparry Lime-rock—which 
_ he placed at the summit of the Transition Graywacke or Taconic 
slate group—to be the stratigraphical equivalent of the Calcif- 
erous Sand-rock of the New York Transition system. Emmons 
had, previous to 1846, concluded that the formation of limestones 
of this sparry type “occurred at intervals during the whole 
period of the deposition of the Taconic slate,” and, acquiescing 
in the judgment of Eaton, now declared that the upper portion 
of the Taconic system,—namely, the great belt of slates with 
limestones, sandstones, and conglomerates,—designated by him 
in 1842 as the Taconic slate, and including both the Transition 
-Graywacke and the Sparry Lime-rock of Eaton, was the strati- - 
graphical equivalent of the lower part of the Champlain division, 
and in fact a thickened and modified form of the Calciferous 
Sand-rock, which was now said to be, in its eastern extension, 
“ protean” in its character, and to include a great variety of rocks. 
§ 14. For the better identification of this Taconic slate group it is 
important to note that Emmons, who had already, in 1842, clearly _ 
defined its eastern and western limits in New York, and declared 
-that it had been traced north and south a distance of one hundred 
and fifty or two hundred miles, repeats with detail, in 1844, the 
facts of its distribution. It is described as occupying geographi- 
cally the interval between the overlying Loraine shales,—the 
_ upper part of the Champlain division,—on the west, and “the 
great mass of the Sparry limestone,” which forms its eastern 
border, and itself lies at the western base of the Taconic Hills; 
which are made up of the three lower members of the Taconic 
em. He now sdas that “the Taconic slate, with its subor- 
