118 Mr Robert Were Fox on certain 



pressure of the sea water acting on the fresh.* Nearly two years 

 ago, I stated in this room, my views in reference to the operation of 

 this latter cause on land springs ; and at the same time, I attempted 

 to shew the possibility, not to say probability, of steam existing in 

 fissures below the water at a very great depth. I may, perhaps, be 

 permitted to refer again to this subject, because it appears to me to 

 be one of some interest. I then took it for granted that the tem- 

 perature of the earth increases, in some proportion, to the increase 

 of depth below its surface ; and that if the ratio be taken at 1° 

 Fahrenheit for every 48 feet, as found in our deep mines ; and if Lo 

 Roche's data for calculating the elastic force and density of steam bo 

 adopted, the forces of steam and of water pressure would balance 

 each other at rather more than nine miles deep, each being equal to 

 the pressure of more than 1400 atmospheres. The density of the 

 steam would there be about one-fourth^ that of water at 60° Fahren- 

 heit, and its temperature above 1050° Fahrenheit. But the tem- 

 perature may probably not increase so rapidly as this at great depths, 

 and the equilibrium in the pressures of the column of water, and of 

 steam, may occur much further below the surface, where the density 

 of steam, under an augmented pressure of water, would, of course, be 

 still greater. However this may be, it would seem that, under any 

 probable circumstances, in regard to the ratio of increase in the 

 earth's temperature, the increase in the pressure of the lengthened 

 column of water would not keep pace with the rapidly increasing 

 tendency of the water in descending into more heated parts of the 

 earth to expand into steam, the elasticity of which, at very high tem- 

 peratures, when confined and in contact with water, is greatly aug- 

 mented by very small increments of sensible heat. 



No water could long remain unchanged into steam below the line 

 of division between them, and there the steam would be denser 

 than at any deeper station, for it would be continually diminishing 

 in density, in descending further from the augmentation of the tem- 

 perature of the earth ; because the expanding influence of the 

 increasing heat would much exceed the condensing influence of the 

 extended column of steam, added to that of the nearly constant 

 column of water. 



The line of demarcation between the water and steam would, 

 doubtless, conform in some degree to the inequalities of the surface. 

 It may be difficult, at first, to conceive the steam capable of sup- 

 porting the water, or rather of existing permanently under it ; but 



* Columns of sea and spring water, above five feet high, balanced 

 against each other in a U-shaped tube, more than a year ago, still re- 

 main unmixed, shewing nearly the same difference of level as at first 

 (exceeding an inch). 



t From some inadvertence, it has been printed in the Appendix to 

 the eleventh Report of the Polytechnic Society, page 2, "/our times" in- 

 stead of ^^ one-fourth" the density of water. 



