T. STERRY HUNT. 45-(15) 



each fifty feet, and thai: at 9000 feet there will be ;in 

 augmentation equal to ISO" P., which added to the mean 

 temperature at the 'earth's surface would considerably 

 exceed 212", the boiling point of water at the ordinary 

 pressure. Now, we are certain that water in the terres- 

 trial circulation descends to much greater depths than 

 this, and thus, in a liquid state, reaches correspondingly 

 higher temperature, at which, as we know from experi- 

 ments made in our laboratories in sealed tubes, its sol- 

 vent powers are greatly and often unexpectedly exalted. 

 In estimating the solvent power of water at gieat 

 depths another principle conies into play, that of the 

 pressure exerted by the column of water, which for each 

 1000 feet in height is equal to thirty atmospheres. The 

 process of solution in water is for most substances attend- 

 ed by contraction, the volume of the solid dissolved be- 

 ing lost in that of the liquid, so that when one hundreth 

 of common salt, for instance, dissolves in water, the con- 

 densation which takes place is far greater than could be 

 brought about in the liquid by any mechanical means at 

 our command — water being nearly incompressible. Ex- 

 periments have, however, shown that external force may 

 aid solution, by favoring this process of condensation ; 

 water under great pressure having been found to take 

 into solution larger amounts of certain matters, such as 

 common salt, than it would at the ordinary pressure. 

 This we should expect to find the case for all such bodies 

 as lose bulk in the process of solution, while the reverse 

 would hold for such as expand in dissolving. The rela- 

 tions of pressure to solution are thus similar to those of- 

 fered by the fusion of bodies under pressure ; by which, 

 as we know experimentally, the melting-point of Such as 

 expand in melting is raised, while for those which contract 

 in melting it is depressed. It is evident then, that hydro- 

 static pressure at considerable depths must cooperate with 

 increased temperature to promote the solubility of many 

 substances in water and in the watery solutions which 

 are circulating through the earth's crust. Of the many 

 chemical reactions which take place at these great depths 

 under the conditions already set forth we can form but 

 inadequate notions. Yet experiments made in the labora- 

 tory of the chemist with heated solutions confined in tubes 

 of glass or of metal have shown that it is possible thus to 



