No. 6. \From the Proceedings of the Royal Institution of 

 Great Britain, 1909, Vol. X/X, p. 243.] 



ICE AND ITS NATURAL HISTORY 



IN a single lecture it will be impossible for me to do more 

 than deal with those points in the natural history of ice which 

 have come under my own notice, and which I have made the 

 subject of special investigation. 



The Nature of the Ice formed by Freezing Saline Solutions. 

 During the Antarctic cruise of the " Challenger," the old 

 question arose as to whether the salt, which is always found 

 in the water produced by melting sea-ice, was present in the 

 solid state as part of the crystalline ice, or in the liquid state 

 as part of the adhering brine. It was one of considerable 

 economical importance to whalers and other mariners who 

 frequent Polar seas. It had been found that freshly frozen 

 genuine sea-water ice was not drinkable. Genuine land-ice, 

 which is easily recognised, gave, of course, good water. The 

 great mass, however, of the ice found floating in Polar seas is 

 of mixed origin. Thus, in its first stage it may be the ice 

 formed by the primary freezing of sea-water. On this falls 

 snow. When there is wind the sea breaks on the edge of the 

 floating ice and throws salt spray over it, which freezes in 

 due time. Hence a piece of sea-ice, picked up at random, is 

 likely to be a very heterogeneous substance ; and no two 

 pieces can be expected to behave exactly alike. It is, there- 

 fore, not surprising that the reports of different navigators 

 regarding the potability of the water formed by melting sea- 

 ice differed. Some maintained that it was undrinkable ; others 

 held that it could be drunk if the first portions melted were 

 rejected, and only the last fraction used. 



In February 1874, when the "Challenger" reached her 

 furthest south, much ice of all kinds was met with, and I took 



