Ill 



composing Formation X., then another series of red shales and 

 soft argillaceous red sandstones, constituting Formation XI. ; and 

 upon these are the coarse quartzose conglomerates of Formation 

 XIL, surmounted by Formation XIIL, or the anthracite coal 

 measures. This last formation, or its equivalent, the bituminous 

 coal measures further west, occupies the highest place in the 

 series of our older secondary or Appalachian rocks. 



The several members of this multifarious group of strata give 

 evidence, from their mutual parallelism, to which there is but the 

 one local exception in the unconformable contact near the Hudson 

 between Formations III. and IV., that they are the results of one 

 strictly continuous series of sedimentary actions. 



Though the chemical agencies which precipitated the lime- 

 stones, and the various currents which introduced into the bed 

 of the same great sea the mechanically suspended materials 

 of the land, gave place to each other in frequent alternations, or 

 underwent, from time to time, a total change, yet do we never 

 find those geological proofs which would indicate an interruption 

 in this prodigious sequence of deposits. Commencing in the re- 

 mote period, which also saw the accumulation of the silurian 

 strata of Europe, their precipitation, unlike that of the latter, was 

 continued, unarrested by any widely influential physical revolu- 

 tions, to the close of that remarkable epoch which witnessed the 

 exuberant vegetation of the coal; whereas, in many portions of 

 Europe an interval of unascertained duration must have elapsed 

 between the elevation of the silurian deposits from their oceanic 

 bed, and the beginning of the new order of things which brought 

 together the materials of the great carboniferous formation. In 

 the region of the Appalachian rocks no pause occurred in the 

 train of sedimentary actions by the elevation and resubmersion of 

 any part of the vast secondary sea. We therefore find, in con- 

 firmation of the other proofs of the absence of such revolutions 

 during the accumulation of the Appalachian strata, that the fossils, 

 the remains of the organic races of that sea, and its shores, exhi- 

 bit a gentler gradation in the changes which they have under- 

 gone as to species, comparing them in the different formations of 

 the series, than is presented when we compare the silurian and 

 carboniferous fossils of Europe. 



