Penny Blood: Serial Sensation and Working-Class Entertainment — page 41: what you’re looking at

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

24 CONDITION OF INTERIOR. — [oH. 11. floats on melted glass, and similarly Bessemer steel on melted steel, and says that Messrs Chance found the castings made from fused Rowley Rag were of the same size precisely as the wooden pattern. It is right to state however that the sand moulds were made red-hot to allow of slow cooling and devitrification’. If we now turn to Mr Hopkins’ “Researches in Physical Geology’,” we find that he had gone into this question some- what fully, and held an exactly opposite opinion to the above. He considered that, so long as the matter of the earth: retained a sufficiently high state of fluidity to admit of the circulation of convection currents, no crust could form: but that when, by those means, the temperature hgd been so far reduced that the currents became arrested, immediately a crust would be formed. “Since the heat increases with the distance from the surface, while the mass is cooling by circulation, the tendency to solidification, so far as it depends on this cause, will be greatest at the surface, and least at the centre. But on the other hand, the pressure is least at the surface, and greatest at the centre; and consequently the tendency to solidify, as depending on this cause, will be greatest at the centre, and least at the surface®.” For want of experimental evidence, “ the only conclusion at which we can arrive is this, that if the augmenta- tion of the temperature with that of the depth be so rapid that its effect in resisting the tendency to solidify be greater than that of the increase of pressure to promote it, there will be the greatest tendency to become imperfectly fluid, and afterwards to solidify, in the superficial portions of the mass: whereas, if the effect of the augmentation of pressure predominate over that of the temperature, this transition from perfect to im- perfect fluidity, and subsequent solidity, will commence at the centre*.” Assuming the latter to be the case, when the mass should have arrived at that stage of cooling that “‘a solid nucleus had been formed, surrounded by an external portion of which the 1 *¢Chemical News,” Vol, xvirr. p. 191. 2 «Phil. Trans. Roy. Soc.” Part m. 1839, quoted in his ‘‘Report to the British Association,” 1847, p. 33. 3 Ibid. | 4. Ibid, — COLA @ (CO) ee SE. ATE A 7° a test Ye. __ to ee oe es eee een ee EE | eet Ee = eee ee, eee ee ee See. a « oa - ee ae ee _ NOOKS