Penny Blood: Serial Sensation and Working-Class Entertainment — page 181: what you’re looking at

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

164 THE REVELATIONS OF [cH. xII, ay for the average rate, that the question we are dealing with is a delicate one, at the same time depending upon data about which we have no very precise knowledge. The thickness may therefore differ from the above results by a few miles, and the temperature by a few degrees either way. But if we are led to seek relief from the somewhat unexpectedly small values, which we have obtained by using the rate A, for the thickness of the crust, (because it will be recollected we have previously assumed it at 25 miles’) and of the melting temperature, 1t seems on the whole that it is to be found rather in assuming a lesser density for the substratum, than in assuming the lower value 4, for the temperature rate’. But with every allowance made for some uncertainty, it must be admitted that the results at which we have arrived are singularly near what on other grounds we may expect to be the truth, while no gra- tuitous assumption has to be made in obtaining them. It is also not unimportant that the two lines of argument in the preceding and present chapters, so diverse in their cha- racters and yet pointing in a like direction, are drawn from observations made in regions as far apart as the Himalayas and the Alps; the conclusion from both being the same, namely that there is a protrusion of the lighter material of the crust into the denser subjacent fluid beneath the mountains in both these regions. If we assume that the relative densities of the crust and subjacent fluid continue the same beneath the ocean as else- where, a reference to the nght-hand side of the figure gives for k, the least thickness of the crust, which in this case will be beneath the ocean, because it is everywhere thickened beneath the continents, k=c—6— (8 - 4 —P_ pi o—p =¢— g—t }. Ep 1 Chap. X. p. 126. 3 For reasons for supposing ,, to be rather below than above the average rate, see p. 16. COMICOOOLKS @ (CO)