48 
OPINIONS OF GEOLOGISTS 
along the Berkshire valley and the ridges east; the granular Berkshire marble was identi¬ 
fied with the blue limestone of the Hudson valley, but metamorphosed by heat; and the 
associated micaceous, talc-ose, and other schists were referred, in the language of the com¬ 
munication, to the slates of the lowest formation of the Appalachian system, while the 
semi-vitrified quartz rock of the western part of the Hoosic mountains was stated to be 
nothing else than the white sandstone (Potsdam sandstone) of the same series slightly 
altered. I am gratified to find from Prof. Mather that these views of identity are embraced 
by him, as they now are, if I mistake not, by Prof. Hitchcock. Prof. Mather indeed says 
that he has traced this slate (Hudson slate) through all its gradations into talco-argillaceous 
and talcy slate, and into graphic and plumbaginous slate; the limestone from compact, 
sandy and slaty, to sparry, slaty, talcose, and crystalline limestone, within short distances, 
and the Potsdam sandstone to a hard compact and granular quartz rock. It is true, Prof. 
Emmons has presented in his report a series of sections of the strata, exhibiting an uncon¬ 
formity at the passage of his Taconic into the rocks of the Champlain division ; but I must 
take the liberty of expressing my disbelief of the existence of any such unconformity, and 
of observing that in the prolongation southwestward of this altered and plicated belt as far 
as the termination of the Blue ridge in Georgia, a distance of one thousand miles, no 
interruption of the general conformity of the strata has ever met the observations of my 
brother or myself.” 
Prof. Rogers then goes on to say, that the Potsdam sandstone forms the base of the 
palaeozoic strata in the latitude of Lake Champlain, or at least in the region of the Mohawk 
river ; and that although there are members of the same family expanded downwards in 
a conformable position in some portions of the Blue ridge district, still the white or Potsdam 
sandstone is yet the most ancient depository of organic life hitherto discovered in our strata. 
We have, then, in the above extracts, Prof. Rogers’s views of the Taconic system, which 
may embrace a few beds older than the Potsdam sandstone; but as these beds are con¬ 
formable to whole and entire series above, they are by no means entitled to the rank of an 
independent system. 
Having now shown how little favor the Taconic system has received from the opinions 
of American geologists, I deem it proper to lay before the reader the opinions of some 
European geologists upon what I consider to be, at least in part, the same system, though 
known under the term Cambrian. All I have to say in this place in regard to the existence 
of such a system in Europe, is to state the conclusions of geologists in relation to it; and 
this I propose to do by extracts from the Address of Air. AIurchison, President of the 
Geological Society of London, delivered at the Anniversary ATeeting on the 18th of 
February, 1842. Omitting several paragraphs which relate only generally to the subject, 
I commence with the following : 
“ If then our researches teach us that the term Cambrian must cease to be used in zoolo¬ 
gical classification, it being in that sense synonimous with Lower Silurian , we see the true 
value of having established a type like the latter, which being linked on through inter- 
