of the States of New York and Pennsylvania. 367 



This leads me again to the consideration of the alternating 

 series in Pennsylvania, composed largely of red sandstones 

 and red shales, with beds of sandstone conglomerate and of 

 limestone, and some bituminous coal, mostly arranged in 

 double anticlinal and synclinal order, as exposed to observa- 

 tion between the bituminous coal ranges of the Alleghany 

 mountains on the west, and the anthracitous coal region of 

 Schuylkill, &c. on the east. Had not Mr. R. C. Taylor de- 

 nominated this alternating series transition, and the red sand- 

 stone immediately underlying the Alleghany bituminous range 

 old red sandstone, judging merely by the evidence produced, 

 and reasoning from analogy, I should have been induced to 

 consider them as the prototypes or representatives of the class 

 of beds which appear in the northern face of the Alleghany 

 mountains, and which I have designated as No. 3 ; both in fact 

 appearing to form the immediate support of the more produc- 

 tive coal-bearing measures No. 4. No evidence is given by 

 the accompanying fossils to prove that this alternating series 

 belongs to the transition period. On the other hand, it is ad- 

 mitted by the author (p. 409.) that this alternating series com- 

 prises four or five troughs or basins containing coal, which on 

 the eastern side of the State of Pennsylvania is anthracitous, 

 and on approaching the S.W. contains upwards of 16 per cent, 

 of bitumen and volatile matter ; while some of the anthracitous 

 beds pass into bituminous coals in certain places (p. 408). This 

 fact affords an argument on the other side, as no well authen- 

 ticated instance exists, so far as my knowledge extends, of a 

 bed of bituminous coal having ever yet been found within the 

 limits of the transition system. 



This is not a question of mere theoretical speculation, but 

 one of high practical importance, as connected with geological 

 investigation and the ceconomical purposes of life; and from 

 the zealous researches now understood to be in progress, both 

 in the State of New York and in Pennsylvania, we may rea- 

 sonably expect that a fuller light will soon be shed upon the 

 subject; in effecting which the successful labours of Mr. R. C. 

 Taylor will no doubt appear conspicuous. 



To what extent transition rocks may occur in Pennsylvania 

 within the area circumscribed by the anthracitous range on 

 the east, the bituminous range on the west, and by both con- 

 jointly on the north, remains yet to be proved. Should such 

 appear within that space, it may require some caution not to 

 confound simple contact with a portion of the carboniferous 

 series, with an arrangement coordinate with the latter. 



A clear exposition of all the relations of the transition system 



