Penny Blood: Serial Sensation and Working-Class Entertainment — page 38: what you’re looking at

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

CH. 11.} CONDITION OF INTERIOR. 21 of the density would vary as the increase of the pressure’. Now the actual ellipticity being known by measurement to be gf; it is highly probable that the law of density above in- dicated expresses a close approximation to the truth. The conclusions here enumerated are the results of re- markably refined mathematical investigations which have exercised the ingenuity of the greatest masters in the science, and the methods and results of which will be found collected in the work by Archdeacon Pratt just referred to. To guide us in our reasoning concerning the condition of the interior we have then the following data: The observed rate of increase of temperature near the sur- face is perfectly compatible with the existence of such a tem- perature within the earth as would fuse all known substances, and fused substances continue’ to flow up from below, and, what is more, there is almost positive evidence that the earth was at one time wholly fluid. The question arises, does this fluidity still normally exist within it, wholly or partially ? The true law of increase of temperature is inextricably mixed up with this other question of the condition as to solidity or fluidity of the interior; because any law of increase of temperature is compatible with the law that the increase is proportional to the depth near the surface. For if we represent the law of temperature by a curve starting from the surface whose axis of abscissa 1s vertical, this merely amounts to saying that any number of different curves may be drawn which have the same tangent at the origin. But the law of increase of tem- perature below that outer part or crust of the earth, which we know to be solid, will be governed by the laws of convection if the interior be fluid, modified by change in the value of gravity, - and by those of conduction if it be solid. Hence if there be a change of state from fluid to solid, there will necessarily be a break in the law at the depth where that occurs; and it will then be further complicated by the thermal changes which accompany the change of state. Now the question as to whether the interior of the earth is at the present time solid or fluid, or partly solid and partly fluid, 1 Pratt’s ‘‘ Figure of the Earth,” 4th ed, Arts, 115—118. CONNEC OOO @ (CO)