290 In and Around the Morteratsck Glacier : 



then being done by Professor Forel of Lausanne, and others, 

 I believed that my work on the lowering of the freezing-point 

 of water in the presence of even minute quantities of foreign 

 matter dissolved in it, and the consequent depression of the 

 melting-point of pure ice when in contact with such water, 

 would find a fruitful practical application in the study of 

 the glaciers. 



The account of these researches was published under the 

 title, ' On Ice and Brines,' in the Proceedings of the Royal 

 Society of Edinburgh for 1887. (See above, p. 130.) 



The principle which guided this research was the follow- 

 ing : If the crystalline body which is formed when a non- 

 saturated saline solution is partially frozen is pure ice, then 

 pure ice of independent origin, such as snow, must, when 

 mixed with the same saline solution, and heat is supplied, 

 melt at the same temperature, -when the concentration is the 

 same. 



The experiments undertaken with this end showed con- 

 clusively that the crystals formed by freezing a non-saturated 

 saline solution are at least as free from salt as freshly fallen 

 snow is, and that therefore the saline matter, from which they 

 cannot in practice be freed, exists in solution and belongs to 

 the adhering brine. 



It was not until this had been established, in 1887. that it 

 became legitimate to say : " The freezing-point of water is 

 lowered by the presence of salt dissolved in it," instead of 

 saying : " The freezing-point of a saline solution is so much 

 lower than that of pure water." 



The former of these statements expresses the fundamental' 

 principle of cryometric chemistry. "In fact the temperature 

 at which ice melts in nature depends on the medium in which it 

 melts as well as on the pressure to which it is subjected. If the 

 pressure is constant, it varies with tlie nature of tJie medium ; 

 and, if the nature of the medium is constant, it varies with the 

 pressure? 



By a curious coincidence, the study of the freezing-point 

 of saline and other solutions in very high dilution (infinite 

 dilution was aimed at), was taken up at this time and 



