IS OPINIONS OF GEOLOGISTS 



along tin- Berkshire valley and the ridges east ; the granular Berkshire marble was identi 

 Bed with the blue limestone of the Hudson valley, but metamorphosed by beat ; and the 

 associated micaceous, lalcose, and othei schists were referred, in the language of the com- 

 munication, i" the slates of the lowest formation of the Appalachian system, while the 



semi-vitrified quarts rock of the western pari of tin- lloosic mountains was staled to be 

 nothing else ilian ilie white sandstone ( Potsdam sandstone) of the same series slightly 

 filtered. 1 am gratified to find from Prof. Mather that these views of identity are embraced 

 by him, as they no* are, if I mistake not, by Prof. Hitchcock. Prof. Mather indeed says 

 that be lia^ traced this slate (Hudson slate) through all its gradations into talco-argillaceoua 

 and talc] date, and into graphic and plumbaginous slate; the limestone from compact, 

 sandv and *lat\, to sparry, Blaty, talcose, and crystalline limestone, within short distances, 

 and the Potsdam sandstone to a haul 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 Ins Taconic into the rocks of the Champlain division; but I must 

 take the Libert] of expressing m] disbelief of the existence of any such unconformity, and 

 of observing that in the prolongation BOUthwestward of this altered and plicated lielt 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. Rom ks then goes on to say, that the Potsdam sandstone forms the base of the 

 pakeoaoic strata in the latitude of Lake Champlain, or at least in the region of the Mohawk 

 ri\er : and that although there are members of tin; same family expanded downwards in 

 a conformable position in some portions of the Blue ridge district, still the white or Potsdam 

 sandstone i- \et 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 pari, the same system, though 

 known under tin- oi in Cumbrian. 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. Mubchisoh, 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 lis that the term Cambrian must cease to be used in zoolo- 

 gical classification, it being in that sense Bynonimous with Lower Silurian, we see the true 

 value of having established a type like the latter, which being linked on through inter- 



