INVERSION OF THE STRATA NEAR THE AXIS EXPLAINED. 
463 
matter, or is so metamorphosed that the earliest traces of life which can be ob- 
served occur in the carboniferous strata. Accurately and rigidly to determine the 
boundaries and passages of such highly mineralized products, must be the result of 
long and minute geological labour. We have chiefly restricted our efforts to the 
development of the original constitution of the chain, and the enormous amount of 
metamorphism and disturbance which large portions of it have undergone. 
One of the facts most worthy of the attention of geologists which have been ob- 
tained by researches in the Ural Mountains, is the very frequently inverted dip of 
the strata where they approach the axis ; the formations, which we know to be of 
younger age, being, as it were, succeeded in ascending order by those which were 
deposited before them. This plisenomenon, far from being peculiar, is, however, 
of frequent occurrence along the sides of other ridges, where masses of eruptive 
matter have been ejected in the contiguity of sedimentary deposits. We have 
before adverted to a similar phenomenon upon the northern flank of the Eastern 
Alps 1 , where the cretaceous and Jurassic deposits along a line of great extent, are 
so inverted, as to dip under the crystalline and more ancient rocks, and a like 
order is well known to those who have examined the Alps of Savoy. In a former 
publication we accounted for the inversion of the Silurian strata on the western 
flank of the Malvern Hills, in the manner suggested many years ago by Mr. Leonard 
Horner, by supposing that those strata were not only raised into a vertical position 
by the outburst of the contiguous syenite, but were also thereby thrown further 
over or backwards 2 . Such an explanation may, doubtless, suffice in cases analo- 
gous to the example of the Malvern Hills, where the same strata can be followed 
from inverted to vertical, and therefrom to normal positions. In the much grander 
examples, however, of the Alps and the Ural Mountains, where long linear masses 
occur in such positions on several 'parallels and at considerable distances ft om the 
great axis of eruption, it would seem that an easier, if not more rational solution 
of the problem is offered by supposing, that the emission of as much molten matter 
from the interior of the earth as would form the chief and central ridges of the 
mountains, may have left cavities occupied for a time only by gaseous vapours, into 
which the ends of the strata, fractured on lines parallel to the line of disturbance, may 
have fallen, thus producing their inverted position by a simple movement of lateral 
depression towards the cavity left by the outburst of the erupted masses. In other 
5 Geol. Trans. Old Ser. vol. i. p. 281; and Silur. Syst. p. 423. 
3 o 2 
1 Geol. Trans, vol. iii. p. 303. 
