TRANSACTIONS OF THE SECTIONS. 69 



enormously rapid ratio as the 4^ power of the temperature, very nearly. The pressure 

 with the latter temperature, viz. 409 lbs. to the square inch", is the highest limit of 

 present exact knowledge. What the pressure is at the greatest temperatures attain- 

 able we do not know, but we have some indications that at a high temperature it is 

 veiy great indeed. The Bev. John Michell * states that in casting two brass can- 

 nons, " The heat of the metal of the first gun drove so much damp into the mould of 

 the second, which was near it, that as soon as the metal was let into it, it blew up 

 with the greatest violence, tearing up the ground some feet deep, breaking down the 

 furnace, untiling the house, killing many spectators on the spot with the streams of 

 melted metal, and scalding many others in the most miserable manner." These great 

 effects were evidently all produced by the steam of a few ounces of water only, for 

 it is called merely "damp. ' It must therefore have been verypowerful steam. Now 

 the temperature of melted brass is known to be only 18(39° F., which would be re- 

 duced by absorption of latent heat, and by raising the temperature of the damp, and 

 the mould, and the neighbouring sand. But the heat of melted stone or lava is 

 3000° F., or, according to some, 3200° F. And since the Gulf of Santorin in the 

 Grecian Archipelago lias been for 2000 years a scene of volcanic operations!, it ap- 

 pears the mass of fire below is so very vast that the sea has not been able to quench 

 it, and therefore the heat of the steam will closely approach to 3000° or 3200° ; for 

 the water scarcely reduces even the surface temperature of so prodigious a mass ; 

 radiation instantly replaces the heat abstracted, by other heat. Since, therefore, 

 saturated steam or its constituents is so very often present in all species of natural 

 disturbances of the earth's crust, it is worth while to remember, on the bare chance 

 of the pressure continuing to increase as the 4J power of the temperature, that in 

 that case saturated steam of the highest temperature would have a force of at least 

 a thousand tons per square inch, which would be .amply sufficient to cause the 

 greatest effects of earthquakes aud volcanos. M. Regnault says (p. 619) that the 

 graphic curve by which he represents hia pressures and temperatures '■ presente un 

 point d'inilexioii " at 627°-2 (J. = 1160°-96 F.J " Enfin," says he, "la courbe, qui 

 toiu-nait sa convexite vers l'axe des temperatures," up to the temperature named, 

 a toume sa eoncavite vers ce meme axe, a partir du point d'inflexion, Toi-donnee 

 tend vers un maximum, et la courbe a pour asymptote, une ligne parallele a l'axe 

 des temperatures, dont l'ordonne'e est. . . . 121617 atmospheres," which are equal 

 to about 800 tons per square inch. " Ce serait done la LVlimite superieure de la force 

 elastique de la vapeur." As far as he can judge. But he very properly adds, "' Mais il 

 serait a mon avis tout a fait deraisonnable d'attacher une signification reelle a ces 

 points singuliers de la courbe, qui sont si loin en dehors des limites on nos obser- 

 vations peuvent atteindre." Supposing he is correct in saying that steam pressure 

 may continue to increase up to about 800 tons per square inch and no higher, that 

 force would still account for the greatest effects of earthquakes and volcanos. 



The volume of steam compared to the volume of water which produced it when 

 the pressure is 26^ lbs. to the square inch, is known to be about 941 times as great, 

 whilst, when the pressure is 606 lbs., the volume of steam is known to be only 

 about 432 times as great as that of the original water §. And the author of the 



Saper thought that heat compresses steam in the same way, though not in the same 

 egree, as the force-pump compresses water in the hydrostatic press ; and that sup- 

 posing the strength of the containing vessel unlimited, and the supply of water 

 sufficient to saturate the steam, the force or pressure attainable would only be 

 limited by the maximum heat in one case, and the maximum pumping power in the 

 other ; and the conclusion he arrived at was, that steam certainly operates quantum 

 valeat in producing earthquakes, volcanos, and other similar disturbances ; and that 

 other forces cooperate, where no help is required. 



He classified the seventy evidences from Humboldt, Lyell, and other authorities 

 under the following heads : — 1. The contact of the metalloid bases with water and 

 air may be a cooperating cause in volcanic processes. 2. Ejections of steam from 



* Phil. Trans. Eoy. Soc, 1760, vol. xi. p. 458. 

 t Lyell's ' Principles of Geology,' 1853, p. 441. 

 % 1141° is the heat of a common fire. —Darnell. 



§ Useful Information for Engineers, second scries, by Dr. Fairbairn, LL,D., F.E.S., 

 p. 313. 



