126 ; GEOGNOSY AND GEOLOGY. 
against one of sandstone, and both be overlaid by a bed of keuper, then the 
latter is said to overlap the others. 
As already mentioned, stratifications are divided into conformable and 
non-conformable. Conformity may exist either in a parallelism of the 
planes of stratification (as p/. 43, figs. 3 and 5), or in an equal extension of 
the strata, as a and a (fig. 3). Non-conformity exists where the strata 
neither exhibit parallelism nor fall i1 use same plane, as seen in fig. 6. 
Here A, B, C, D, have different positions from F and H, although A, B, C, 
are conformable to each other, as also are F and. E. 
12. Order of Succession and Relative Age of Rock Beds. 
- Long continued and careful observation has shown that a constant order 
exists in the succession of different rocks, and one that is never departed 
from. This is especially the case with the stratified masses (those formed 
by successive deposition from water). Thus we find strata of muschelkalk 
lying on variegated sandstone, and keuper on muschelkalk, and this 
succession occurs wherever these rocks are found; if they were to be 
continued round the earth, they would embrace it concentrically, like the 
coats of an onion. This condition, to a certain extent, would, in fact, have 
existed, but for the interference of volcanic or volcanoid actions; these 
have elevated large islands, and even entire continents, from the bottom of 
the former universal sea, and thus prevented any further deposit on these 
portions of the ancient ocean bed. It is only where water occupied large 
basins that this could occur. The strata thus formed we find to be 
interrupted by non-stratified rocks, these sometimes spreading above them, 
just like the lava streams of modern times, which, after fillmg up deep 
ravines, run over the edges, and are diffused over the surrounding country. 
The correctness of this analogy is shown, not only in the above relation, 
but also in the petrographical condition and structure of ancient and modern 
igneous rocks. It is upon these diversities of existence of the different beds 
of rocks that the difference between normal and abnormal masses has been 
grounded (exogenous and endogenous of A. von Humboldt). The former 
are the really stratified, the latter those which were once in a melted 
condition. Inasmuch as we are permitted to assume that all normal masses 
have been deposited from water, we are entitled to consider their order of 
succession as indicating their relative antiquity; a rock is then older than 
the one above and younger than the one below it. An absolute 
determination of the antiquity of strata is impossible, even approximately ; 
this much is, however, certain, that the oldest proclaims an age which vastly 
exceeds that of 6000 years. 
To determine the relative age of masses, which, genetically considered, 
must be supposed to have been forced up from below, it is necessary to 
pursue a different method; we cannot, of course, determine from the actual 
succession in this instance. In this case we must have reference to the 
penetration of one abnormal mass by another, and that of normal by 
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