76 
GEOLOGY 
ings of the Association of American Geologists. Boston. 1843.)*, a wave theory to explain the folding and 
orography of the Alleghanies, and further he has tried to extend that explanation to the Alps, the Jura, 
or to any other Chain of Mountains (See: On the Laws of Structure of the more Disturbed Zones of the 
Earth's Crust, page 431 etc., in the Transactions of the Royal Society of Edinburgh, vol. XXI, part III. 
Edinburgh, 1856.). From what I have observed in crossing the Alleghanies, I am far from admitting 
the theory of Rogers not only as to the details, but even in its main features; and geologists must wait 
until there is a good topogi'aphical map of the Alleghanies , before they can have just and exact ideas 
as to that beautiful chain of mountains. I must add that hypothetic and doubtful as the discovery of 
Rogers is, it has been claimed with some justice as the discovery of J. D. Whclpley and A. A. Hender- 
son, formerly assistants in the Geological Survey of Pennsylvania; see: Manual of Coal and its Topography , 
by J. P. Lesley, page 123 etc.; Philadelphia, 1856. Lesley, in that interesting work, says: « That the 
((European Jura, although the home of geology for at least a century, had to wait for its elucidation 
((Until the American Appalachians had been mapped, may seem strange, but it admits of easy expla- 
(( nation)). And also: ((The region of the European Jura resembles it in general structure, and exhibits 
«the ancient action of similar forces under the same laws, but in less detail, and with far less delicacy. 
« The author was fortunate in being the first geologist who had an opportunity to approach the dynamic 
((phenomena of the Jura with an American eye trained on this typical ground. This was in 1844; Mr. 
((Rogers did the same in 1849 ». I am sorry not to agree w'ith Lesley as to his being the first to ex- 
plain the dynamic phenomena of the Jura, and if the one chain of mountains was to be elucidated by 
the other , it is the Alleghany that must be explained by the Jura. Jules Thurniaim published his ex- 
cellent and beautiful theory of the dynamic phenomena of the Jura in 1832, under the title of: Essai 
sur les SouUvements Jurassiques du Porrentruy (Jura Bernois), Paris; and Lesley, Rogers, A\helpley, and 
Henderson were probably acquainted with that work when they began their Geological Survey of Penn- 
vania in 1836 [First Annual Report of the State Geologist', Harrisburg, Pennsylvania.). Thunnann w'as 
prudent enough to limit his theory to the Jura mountains; and in his posthumous work, now in the course 
of publication at Geneva: Essai d'Orographie Jurassique, in 4°, 1857; he gives more true knowledge and 
facts concerning the dynamic and orographic phenomena of the Jura, than have ever been given upon 
any chain of mountains. 
Many parts of the Alleghanies, especially in Virginia, North Carolina, and Georgia, contain auri- 
ferous quartz and itacolumites, which yield a profit to the miner, and have not been abandoned even 
since the discovery of the Placeres of California and Australia. 
The group known under the name of the Ozark mountains belongs to this system of dislocation of 
the Alleghanies ; it was formed about the end of the deposit of the Coal series , which it elevated and 
dislocated in the same direction, North-East and South-West. Only there is an esse^^tial geological dis- 
tinction to establish upon what is called the Ozark mountains. Geographers, and especially Major Long 
(See: Account of an Expedition from Pittsburgh to the Rocky Mountains, performed in the years 1819 and 
1820» two voL, 8°, with an atlas; Philadelphia, 1823.), who first made a scientific exploration in those 
regions, have comprised under the term Ozark, all the mountains found between the Mississippi, 
Kansas, the Prairies, and the Red river. But we have seen above, that 1 refer to the Lawrentine 
system several masses of granitic mountains which are comprised in the limits indicated, and which run 
E. 5° N. , and W. 5° S. The Carboniferous rocks repose horizontally at the foot of those granitic masses 
which they surround, and consequently the dislocations which they have undergone in these regions 
are much later than the appearance of these islets of eruptive rocks. Besides, the directions of the 
ruptures and upheaval of the Coal measures are altogether different, and coincide with those of the Al- 
leghany system. 
The chains of mountains forming the Ozark system, properly speaking, exclusive of the granitic 
masses of Fort Washita. Little Rock, and Potosi, are composed of parallel lines running from North-East 
to South-West, with a slight deviation towards the north, and having a breadth varying from 100 to 
