Land-tracts during the Secondary and Tertiary periods. 167 



distance of 400 miles from the Irish shore, ridges of consider- 

 able elevation apparently parallel with the line of Portugal and 

 England, terminating with an abrupt declivity of upwards of 

 7000 feet, which would appear to be the western escarpment of 

 the Anglo-Portuguese system. Crossing the immense valley 

 which is occupied by the Atlantic between this point and the 

 American shore, we find a magnificent development of parallel 

 secondary movements in the Appalachian chain and the deposits 

 flanking it. The elaborate surveys, by the State surveyors, of the 

 Atlantic border of the Appalachian chain, and of that chain itself, 

 enable us to speak with precision of the phenomena attending 

 the development of the secondary formations of that region. 

 The parallelism of the ridges into which the palaeozoic deposits 

 have been thrown in the Alleghanies is perhaps even more 

 marked and persistent than in the Oural chain ; and the persist- 

 ence of outline of the shore of the secondary oceans, exhibited 

 by the successive outcrop of the secondary formations along the 

 littoral border of the Alleghanies, is almost uninterrupted, and 

 so nearly coincides with the present Atlantic shore, that if the 

 whole region were now to be depressed to the level it occupied 

 during any age of the secondary period, the sea would again wash 

 a coast-line agreeing in its main features with the outcrop of the 

 formation of that age. We see represented here the same fea- 

 tures that occur in England and Erance, viz. the return of sea 

 after sea, from the Jurassic down to and including the older ter- 

 tiaries, to the same, though in most cases shrunken, bed as that 

 occupied by its immediate predecessor. This is most conspicuous 

 in Virginia and the States to the south of it, the outcrop of the 

 tertiary and secondary strata successively disappearing under the 

 Atlantic as it advances northward. Here also we see that suc- 

 cessive desiccation to which I have adverted in the case of Eussia 

 and England and Portugal ; but the succession is less regular 

 in the Alleghany region, the newer secondaries more generally 

 overlaying the older, and exhibiting a greater alternation of level 

 than is the case in Europe ; indeed so considerable has this alter- 

 nation been, that the equivalents of the middle secondaries of 

 Europe have not been well made out, being mostly either absent 

 or else hidden by the overlay of the newer secondary (cretaceous) 

 deposits. 



The investigations and explorations of Marcou, Shumard, 

 Swallow, Heyden, Meek, and many other American geologists 

 and explorers of the formations on the western flank of the Ap- 

 palachian chain warrant an inference that the secondary sea, 

 particularly during the cretaceous periods, swept round the 

 southern termination of the chain and filled the area now occu- 

 pied by Texas, Kansas, and the Indian territory, extending thence 



