244 Mr. J. Y. Buchanan [May 8, 



melted ice. The advantage of fractional melting for the purpose of 

 obtaining water of less salinity was confirmed ; but it was found im- 

 possible, by any means, to produce pure water by melting the ice. 

 This, combined with the fact that its melting-point was considerably 

 lower than that of pure ice, was for me convincing evidence, at that 

 date, that the salt was present in it in the solid state, and that, con- 

 sequently, the crystalline body formed by freezing sea-water and 

 similar saline solutions was not pure ice. 



About ten years later Dr. Otto Pettersson's treatise * on the 

 properties of water and ice came before me, and I studied it with 

 great interest. In it he refers to my " Challenger " work, and rejects 

 the view that " sea ice is itself wholly destitute of salts, and only 

 mechanically encloses a certain quantity of unfrozen '•and concentrated 

 sea-water." I was much gratified to find that he had, quite independ- 

 ently, arrived at the same conclusion as I had. 



In the careful study which I made of his work, the following 

 passage, p. 818, arrested my attention : '• A thermometer immersed in 

 a mixture of snow and sea-water which is constantly stirred, indicates 

 -1*8° C." If this statement was exact, it was clear that the evidence 

 furnished by the melting temperature of the sea ice was not entitled to 

 the weight which I had attached to it, and that the conclusion, at 

 which we had both independently arrived, was open to doubt. On 

 making the experiment, I was able to confirm his statement. I 

 thereupon decided to proceed without delay to investigate the subject 

 experimentally. 



The question at issue concerned saline solutions generally, 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. f 



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 concen- 

 tration is the same. 



The result of the research was definitively to establish the validity 

 of this principle on experimental evidence. 



* On the Properties of Water and Ice ; by Dr. Otto Pettersson : Publica- 

 tions of the " Vega " expedition, 1883. 



f The results of the research, which I began in the year 1886, were com- 

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

 ' Nature,' 1887, xxxv. j)- 608, and xxxvi. p. 9. The whole subject of the 

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

 HoO 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. 



