Penny Blood: Serial Sensation and Working-Class Entertainment — page 114: what you’re looking at

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

“% oe CH. VIII. ] FLUID SUBSTRATUM. 97 In our ignorance of the properties of water at the high temperatures and under the pressures we are now considering, it is not possible to arrive at any but the most general con- clusions. If we take the mean depth of the ocean to be 2500 fathoms, we find that the pressure due to a layer of water of this depth would be 442 atmospheres, or 336424 mm. of mercury. But we must reduce this in the proportion of 146 : 197’, because the depth will be inversely proportional to the area, and we are now sup- posing the ocean spread over the whole globe. This will make the pressure about 327 atmospheres or 249329 mm. of mercury. We do not know what temperature corresponds to this pressure. It was found by M. Cagniard de la Tour that the critical tem- perature of water is about 773° F., but the pressure was not determined. At that temperature the water began to dissolve the glass tube which contained it. At the temperature 230° C., or 446° F, the pressure of steam is 20926 mm. of mercury*. This appears to have been the highest determined by Regnault. It is at once apparent that the temperature corresponding to 249329 mm. of mercury must be greatly above the critical temperature. The lower portion only of the aqueous envelope would have been sufficiently compressed to hold silicates in solution. These would have begun to be deposited in a solid and probably 1 Ch. v. p. 54. £ Balfour Stewart’s ‘‘ Heat,”’ 2nd ed. p. 402. Locomotive engines are con- structed to work up to a pressure of about 10 atmospheres. Extract from a letter by Mr J. Aitken in “‘ Nature,” vol. xx111. p. 84, 1880 :— ‘A free surface is any surface of the body under examination at which it is free to change its state.”. ... ‘‘As to what the freezing, melting, and boiling points are when these free surfaces are absent, we have at present no knowledge what- ever. All we know is, that the freezing point is lower, and the ‘‘melting’’ and ‘‘boiling points” are higher, than when free surfaces are present. The first of these points is too well known to be referred to here. The last point was illus- trated in the paper referred to” (Royal Scottish Society of Arts, 1874~5) ‘‘ by an experiment in which water was heated in a metal vessel under atmospheric presstfre to a temperature far above ‘the boiling point,’ when the water exploded and violently ejected itself from the vessel. The superheating of the water was accomplished by carefully excluding all free surfaces, by bringing the water into as perfect contact with the metal of the vessel as possible.” F. 7 NOO COLA @ (CO)