Penny Blood: Serial Sensation and Working-Class Entertainment — page 299: what you’re looking at

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

282 SUMMARY. " [cH. XXII. oceanic crust may be about 2°955; that its thickness 1s there about 20 miles; while, in the continental areas, its density is about 2°68, and its thickness at the sea level about 25 miles. XIII. We cannot explore the sub-oceanic crust, and do not know from direct evidence whether it has been compressed, as we know has happened to the continental areas. Many geologists feel assured that the oceanic areas have always been oceanic, and that they have never interchanged places with the continents, If that be the case they have never been com- pressed and elevated. Referring to the two modes in which compression may have caused elevation, namely, by either raising the crust into anti- clinals, into which the subjacent denser fluid would rise, or by producing ridges on the surface, which would be accompanied by corresponding depressions of the lighter crust, into the fluid beneath, we remark that, if the former were the arrangement, the two phenomena we have lately discussed would be abso- lutely reversed. For the attraction of mountain masses would be greater than if they consisted of matter of the mean density of the crust, instead of being less ; and the increase of tempera- ture would be also greater in mountainous regions, instead of being less. : Compression may have arisen from contraction of the in- terior, or from expansion of the crust, or from these two pro- cesses going on together. We have shown that the contraction of a solid earth through cooling cannot explain the existing inequalities, Neither does it appear that the contraction of a liquid substratum from mere cooling can have been much greater than that of a solid globe, for, before the time when a crust began to form, the liquid must have become reduced by convection to nearly the temperature of solidification ; and sub- sequent cooling, accompanied by solidification and thickening of the crust, would have proceeded downwards, almost as if it rested on a solid nucleus, the loss of heat taking place from the crust alone. In order to estimate the amount of contraction, which would have produced the existing inequalities on the hypothesis of a fluid substratum, we must proceed somewhat differently from CONNEC OOO @ (CO)