1887] o The Taconic Question Restated. 123 
‘supposed to indicate the presence of magnesian silicates. Be- 
sides the three above named, there were, according to Emmons, 
two other divisions, the “ Sparry limestone,” by which he desig- 
» nated the Sparry Lime-rock of Eaton, and the “ Taconic slate.” 
This latter, which he“declared to be quite distinct from the Mag- 
nesian slate, had, according to Emmons, been traced one hundred 
and fifty or two hundred miles, and included another band of roof- 
ing-slates, It is said to be more or less interstratified with lime- 
stones, and “ often becomes a coarse graywacke.” This Taconic 
slate, thus defined by Emmons in 1842 as the uppermost mem- 
ber of his “Taconic system,” is, as will be seen, the First or 
Transition Graywacke series of Eaton. 
Emmons, moreover, at this time calls attention to the fact 
that the Primitive Lime-rock, or Stockbridge limestone, “ being 
often sparry, and of fine texture, is mistaken for the true Sparry 
limestone.” He further remarks that as the succession of these 
disturbed strata is “ unsettled, or at least not so clearly established 
as desirable,” he follows their geographical order in describing 
them, but proceeds to tell us that the “ Taconic slate” group lies 
between the so-called Hudson River or Loraine rocks on the 
west and the Sparry limestone on the east, and, moreover, that 
“it is undoubtedly overlapped by the former rocks, and passes 
beneath the latter with a dip of 30°-35°.” The whole Taconic 
system was further described by him at this time as “the rocks 
lying between the upper members of the Champlain group and 
the Hoosic Mountains,” and was, moreover, regarded “as inferior 
to the Potsdam sandstone, or as having been deposited at an 
earlier date than the lowest member of the New York Transition 
system.”* The precise relations of this Transition system to the 
Silurian and Cambrian systems of the British geologists, and 
indeed the limits of these in England, were not at that date clearly 
understood; but Emmons, in 1842, supposed that the Taconic 
rocks in part might “be equivalent to the Lower Cambrian of 
Sedgwick,” “ the upper portion being the lower part of the Silurian 
system,” to which the Middle and Upper Cambrian were then, on 
the authority of Murchison; very generally referred. That he 
accepted the extreme views of Barrande, and the pretensions of 
Murchison as to the downward extension of the limits of the Si- 
lurian, is shown by the language of Emmons, quoted farther on. 
1 Loc. cit., ppe 140, 144, 163. 
