48 OPINIONS OF GEOLOGISTS 



along the Berkshire valley and the ridges cast; the granular Berkshire marhle was identi- 

 fied with the hhu! limestone of the Hudson valley, but metamorphosed by heat; and the 

 associated micaceous, talcose, and other schists were referred, in the language of the com- 

 munication, to the slates of tlie lowest formation of the Appalachian system, while the 

 semi-vitrified quartz rock of the western part of the Hoosic mountains was stated to be 

 nothino- else than tlie 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. 

 Enunons has presented in his report a series of sections of the strata, exhibiting an imcon- 

 formity at the passage of his Taconic into the rocks of the Champlain division ; but I must 

 lake the liljcrty of expressing my disbelief of the existence of any such unconformit)', 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 ojiinions 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 Mr. Murchison, President of the 

 Geological Society of London, delivered at the Anniversary Meeting 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 Camlnian 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 througii inter- 



