Penny Blood: Serial Sensation and Working-Class Entertainment — page 285: what you’re looking at

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

268 SUMMARY. (cH. xx11. have, at the depth of from 200 to 400 miles, temperatures which would equal those, which have been on good authority attribu- ted to the sun himself. The equable law of increase, however, may be so far depended on, as to lead us to expect a tempera- ture at which the rocks would melt at a depth of not more than 30 miles. IL We are next led to speculate about the condition of the earth's interior. And first we enquire what is the law of density ? The density of the surface rocks can be fairly esti- mated by actual observation in more ways than one, and is found to lie between 2°56 and 2°75 times that of water. The mean density of the whole earth has been determined by ex- periments with the plumbline, and torsion balance, and may be taken to be about 5°5. There is little doubt that the interior of the earth is in a sense stratified, and consists of layers, or couches de niveau, each of equable density, and that the density is greater towards the centre, and diminishes towards the sur- face. But it is not known for certain what the actual law of density is; that is to say, we do not know how great the density is at any given depth, nor how thick any stratum is, which may be supposed to have a particular density. All that we really know is that the heavier layers are deeper down than the lighter, and that the forms of them are spheroidal, becoming more and more flattened about their poles as they approach the outer surface. : Now these are the arrangements and forms which the strata of a liquid spheroid would assume under the action of rotation and gravitation. It has ‘been consequently concluded that the earth was once wholly melted. Here, then, two lines of argument meet. The present law of temperature is such that we may expect to find heat enough at the present day to melt the materials of the earth at the depth of about 30 miles, and mathematical investigations, concerning the figure of the earth and its law of density, lead to the conclusion that it has been melted. The question arises, whether it 1s at this day molten within, either wholly or par- tially, or has the molten condition passed away, so: that it is now solid? There is however a ftertiewm quid. Some have ‘ COMIC OOOKS.EO