Land-tracts during the Secondary and Tertiary periods, 165 



probably was caused) by an entire change in this alignement : 

 the volcanic bands which brought into existence the extensive 

 mountain systems which are formed out of the palaeozoic strata, 

 broken up and thrown iDto parallel ridges of immense extent, 

 obliterating almost entirely the alignement which the palaeozoic 

 strata had previously possessed, appear to have burst forth, not 

 merely in one hemisphere, but over the whole world as far as 

 hitherto examined, in a direction more or less from north to 

 south, and to have maintained this direction during the whole 

 secondary period. These old volcanic bands have left their evi- 

 dences in several great systems which have been examined by 

 competent geologists, and, there is reason to believe, in other 

 mountain chains of similar direction not yet examined. The 

 well-marked and examined systems consist, in the northern he- 

 misphere, of the Alleghanies*, the Ouralf, and of the system of 

 Portugal J prolonged into the North of England; and in the 

 southern hemisphere, of the great system of Eastern Australia § ; 

 of like origin with which appears to be the palaeozoic and schis- 

 tose system of New Zealand ; and lastly, the grand systems of 

 the Kocky Mountains || and of the Andeslf. 



There seems reason also for inferring that the north and south 

 ridges of Central and Southern Africa, crossed by the late tra- 

 vellers in that region (Burton, Speke, and Livingstone), of whose 



it may be added that, according to M. Abich, Bull. vol. xii. p. 116, a great 

 east and west axis, presumably of carboniferous date (being formed of De- 

 vonian rock), traverses European Russia from the meridian of Smolensk to 

 that of the Oural. M. Tchihatchef also describes similar axes running 

 through Galatia and Paphlagonia {Bull. vol. viii. p. 312), and through the 

 Antitaurus {Bull. vol. xi. p. 402). 



* See Rogers, " Physical Structure of the Appalachian Chain," in 

 'Reports of Survey of Massachusetts,' p. 522 (Boston, 1838). See also 

 Report on Geol. Explor. Pennsylvania, 1836, 1838, 1839, 1840, 1841. 

 Report on Geol. Survey of Virginia, 1840, 1841. 



f Murchison, Proc. Geol. Soc. vol. iii. pp. 398, 717. Also ' Siluria, 9 

 pp. 294 to 300, and p. 333. 



X Sharpe, Quart. Journ. Geol. Soc. vol. vi. p. 135. 



§ See Strzelecki's 'Australia/|Lond.l845. See also Odernheimer, in Quart. 

 Journ. Geol. Soc. vol. xi. p. 399. Clarke in same, p. 408. Selvvyn, in 

 vol. x. p. 299 ; vol. xiv. p. 533 (wherein the north and south strike of the 

 palaeozoic rocks and their unconforraability to the secondary coal-bearing 

 strata reposing on them is shown) ; vol. xvi. p. 147. Resales, in vol. xv. 

 p. 497 (showing the palaeozoic strike below the drift). 



|| See Hector, Journ. of Geograph. Soc. I860; Edinb. New. Phil. Journ. 

 vol. xi. p. 169; Quart. Journ. Geol. Soc. vol. xvii. p. 388. Shumard, 

 Trans. Acad. St. Louis, vol. i. No. 3. p. 341. 



IF See Forbes, Quart. Journ. Geol. Soc. vol. xvii. pp. 38, 48. See also 

 Darwin's ' South America ' (1846), pp. 237-248, who at page 247 proceeds 

 thus : — " Hence it would appear that the Cordillera has been probably, 

 with some quiescent periods, a source of volcanic matter from an epoch 

 anterior to our cretaceo-oolitic formation to the present day." 



