I 887] The Taconic Question Restated. 317 
been by many European geologists regarded as altered strata of 
various ages, alike mesozoic and palzozoic, but are, in the opinion 
of Gastaldi, of Jervis, and many others, infra-Cambrian. Rocks 
lithologically and stratigraphically similar occur in Spain and in 
Norway, as I have elsewhere pointed out. 
§ 35. It now became necessary to give distinctive terms to the 
two great groups of strata which, although originally separated 
by Eaton, were at first united by Emmons in one system, after- 
wards divided by him into Lower and Upper Taconic. It is 
unfortunate that the distinctive name of “ Taconic slates” given by 
Emmons to the Upper Taconic division,—the First Graywacke 
or Cambrian,—solely for the sake of distinguishing it from the 
lithologically similar and often contiguous slates of the Second 
Graywacke or Ordovician (with which they had been confounded 
by his colleagues under the common name of Hudson River 
group), should have given rise to the false notion, entertained by 
some, that these Cambrian slates have a better title to the name of 
Taconic than the underlying Magnesian slate of Emmons—with 
its associated roofing-slate or Transition Argillite—and the 
still older crystalline limestones and quartzites ; all of which were, 
together with the “ Taconic slate” group, included from the first 
in the Taconic system of Emmons 
That the Taconic slate group or Upper Taconic was nothing 
more nor less than the Cambrian of the Appalachian valley has, 
we think, been made clear, and that the Lower Taconic is a 
wholly distinct and older ‘series is also apparent. Its granular 
quartzites, often flexible ; its crystalline limestones and dolomites, 
sometimes, like the quartzites, micaceous, and occasionally in- 
cluding amphibole and serpentine ; its schistose beds, intercalated 
throughout, abounding in hydrous, non-magnesian micas, and 
occasionally carrying chlorite, talc, serpentine, garnet, and pyrox- 
ene; the presence also in the series of cyanite, staurolite, tour- 
aiie rutile, diamonds, and graphite; finally, the great included 
beds of magnetite, of hematite, and of siderite and pyrite, both 
yielding limonite by epigenesis,—all serve to show the existence 
of a peculiar and well-defined series of crystalline rocks, which 
are from four thousand to ten thousand feet in thickness, and are 
not less distinct from the uncrystalline Cambrian Graywacke or 
Upper Taconic than from those older crystalline series, the Lau- 
rentian, Arvonian, Huronian, and Montalban; upon each of which, 
