Ice and its Natural History 235 



and, in the research, which I undertook in 1886, solutions of 

 single salts were considered in the first line, and sea-water 

 was included as a particular case of a composite saline 

 solution 1 . 



The principle which guided the research was the following: 

 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 result of the research was definitively to establish the 

 validity of this principle on experimental evidence. 



It was found that when a non-saturated saline solution is 

 gradually frozen, certain crystals, which we call ice-crystals, 

 separate out ; and, during this process, the temperature of 

 the mixture gradually falls, while its concentration increases. 

 When this mixture was warmed, the crystals gradually melted, 

 the temperature rose, and the concentration of the solution 

 diminished. When, in the process of cooling and freezing, 

 the temperature had fallen to a certain point, say /, and the 

 salinity to s, it was found, when this process was reversed, 

 and the same temperature t was reached during the process 

 of warming and melting, that the solution had regained the 

 same salinity s. Therefore, the substance which forms the 

 ice-crystals which separate out at a temperature t during 

 cooling, melts again at the same temperature during warming; 

 and the concentration of the solution at that temperature is 

 the same whether the temperature is arrived at by cooling or 

 warming. 



When a solution of the same salt, having a higher con- 



1 The results of the research which I began in the year 1886 were communi- 

 cated to the Royal Society of Edinburgh in a paper on ' Ice and Brines,' which 

 was read on March 21, 1887, and was published in the Proceedings of the Society, 

 vol. xiv. pp. 129-149. A full account of it was also published in Nature, 1887, 

 vol. xxxv. p. 608, and vol. xxxvi. p. 9. (See above, p. 130.) The whole subject 

 of the influence of dissolved salt on the state of aggregation of the substance water 

 at temperatures below its normal freezing and melting point, and above its normal 

 boiling and condensing point was passed in review in my ' Chemical and Physical 

 Notes' in the Antarctic Manual, 1901, pp. 73-108 (above, pp. 44-68). 



