THE 



AMERICAN 



JOUENAL OF SCIENCE 



3 



&c 



I 



Art. L — RemarJcs on the Geology of the LaJces and the Valley 

 of the Mississippi^ suggested by an excursion to the Niagara and 

 Detroit Riversj in Juhjj 1833; by John Bannister Gibson, 

 Chief Justice of the Supreme Court of Pennsylvania. 



It is known that the principal geological formations in Pennsylva- 

 nia, so far as the series extends, occur in the order of superposition in 

 which the same formations are arranged in Europe, We have, with 

 their subordinates, granite, gneiss, mica slate, clay slate, graywacke 

 including the old red sandstone, transition and mountain limestone, 

 and the great coal formation which traverses the state from north- 

 east to south-west, and which ought by analogy to lie immediately 

 on the mountain limestone, instead of the stratum of rock salt* on 

 which it is proved to lie by the borings on the Ohio and its tributa- 

 J'les, At Pittsbufo^, the salt is found under three distinct seams of 



coal, at an average depth of five hundred feet below the bed of th© 

 river. 



In the north-western part of the state, in the western part of 

 New York, in Upper Canada, Ohio, Michigan, and regions further 

 west, tw^o superior formations oc^cur. The inferior of these, is thq 

 new red sandstone of the English geologists, and is scarcely distin- 

 . guishable by its external character from the old, which has, in this 

 country, been usually confounded with it, although admitted in Eu- 

 rope to be the undermost member of the carboniferous group, if not 

 a ferruginous graywacke. The other, however, is here in place, 

 resting on the basset edo-es of the coal strata which crop out along 



* The statement of the author is doubtless correct as a general fact; but, it may 

 l>e added, that the salt of the West is found also above the coal, as well as below 

 it. See Dr. S. P. Hildreth's memoir and sections in our last number. Salt does 

 not occupy, invariably, the same position in Europe, for it is found both higher 

 and lower than the new red sandstone. — Ed. 



Vol. XXIX.— No. 2 



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