Penny Blood: Serial Sensation and Working-Class Entertainment — page 303: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

286 SUMMARY. (cH. Xx. XVI. Compression is not the only kind of disturhance which has affected the rocks. Faulting is quite as common a phenomenon ; and the amount of dislocation produced by it varies from a few inches to miles. We attribute faults to the formation of fissures, originating at the surface through con- traction of the rocks, and propagated downwards. We attribute their usual hade to the downthrow, to the greater compressi- bility of the rocks on the downthrow side of the fault. Faults on the whole must tend to depress the surface of any tract dislocated by them. Thus it will be seen that the two classes of disturbance which have affected the crust, are ultimately traced to the same exciting cause, namely the formation of fissures through metamorphic changes. When these fissures originate below and are propagated upwards, they become filled with elastic vapour and compression results, and when they originate above and are propagated downwards, faulting is the consequence. XVII. The peculiar arrangement which is requisite for the equilibrium of a disturbed crust resting upon a heavier fluid substratum is, that, for every subaerial elevation above the mean surface, there must be a corresponding protuberance, dipping downwards into the fluid below; and according to the relative densities which we have assumed, the depth of these protuberances must be about ten times the height of the elevations. We have already seen that this circumstance explains two remarkable phenomena, connected respectively with mountain attraction and with underground temperature. We now proceed to show that it also agrees extremely well with many of the well-known geological movements of the surface. As the surface is denuded down, it will be concurrently raised up from below by floatation, and the immense quantity of material denuded off a tract will not require the tract at any one period to have had the altitude, which the amount of denudation at first sight appears to necessitate: nor yet will any additional exciting cause of elevation be required, beyond the mere fact of the denudation. The course of drainage across the dip is also explicable on this hypothesis. COMIC OOOKS @ (CO) a —___ aaa - —— .am -eeee