Penny Blood: Serial Sensation and Working-Class Entertainment — page 309: what you’re looking at

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292 APPENDIX. It will be seen that the facts, upon which Mr G. H. Darwin bases his investigation, are the same as were perceived by Sir G. B. Airy to require explanation. Admitting that the ma- terials of the earth cannot be strong enough to bear the stress, the difficulty was explained by him in the manner given in his own words in our eleventh chapter. If that ex- planation be accepted, the stresses arising from the inequalities of the surface can exist only within the elevated tracts them- selves, which possess no doubt sufficient rigidity to keep them from flowing down into flatness. If the crust is of appropri- ately varying thickness in different parts of the land surfaces, and denser beneath the oceans, and floats in equilibrium on a fluid substratum, it cannot transmit any unequal stresses to the subjacent parts. The other notice referred to appears in the Comptes Rendus de l’Académie des Sciences’, and is by M. Ed. Roche. He points out that “the conditions which every hypothesis ought to satisfy respecting the distribution of the interior mass of the earth are, that it should agree with the value of the superficial ellipticity and also with a certain constant depending upon the phenomenon of precession. These conditions are very nearly satisfied upon the hypothesis of fluidity if we admit that the ellipticity of the earth is about 54,; but if the ellipticity 1s higher than y4,, as appears to result from more recent determinations, the agreement no longer exists.” “There is then room to undertake these investigations again upon a different hypothesis ; for example, by considering the globe as formed of a nucleus or solid block nearly homo- geneous, covered by a lighter layer, whose density from geo- logical considerations may be estimated at three times that of water. This constitution of the globe being premised I find that it is possible to reconcile the actually admitted values of the precession and ellipticity if we take account of the fact that the interior nucleus of the globe is solidified and has received its definite form under the influence of a rotation less rapid than that with which the earth is actually animated.” 1 Tome xcr11. No. 8 p. 364 (22 Aottt, 1881). Paris. commiclsoolkks (CO) FAL |