2l6 AMONGST THE SOUTHERN ICE. 



upper masses of loose or but slightly congealed snow often 

 split off and fell away as the masses floated past. 



The ice was frequently stained of the yellow ochreous tint 

 described by Sir J. D. Hooker, and found by him to be 

 caused by Diatoms washed up on to the ice by the waves, and 

 hanging on its rough surface.* The colouring was always 

 most marked about the honeycombed wash-lines of the ice 

 blocks. Pancake ice is similarly discoloured by Diatoms in 

 the Arctic regions.t 



On February 25th we entered the edge of the pack, sailing 

 amongst some loosened outliers of it. The sea was covered 

 with masses of ice up to 10 feet in length. These consisted 

 mostly of light snow ice, and did not project more than from 

 two to four feet out of water. The upper parts of the masses 

 were composed of white fresh snow, or honeycombed wet 

 frozen snow, which had been partly melted by the waves. 

 Very many of these ice masses were stained of an ochre tint, 

 by Diatoms and other surface organisms. 



The lower submerged ice was transparent, but extremely full 

 of large air vesicles. The ice below the water line, and under 

 the overhanging edges at that level, looked blue. The upper 

 masses were quite opaque. 



I went in a boat to collect discoloured ice. The discoloura- 

 tion appears far less marked when seen at close quarters. It 

 becomes almost invisible when the porous snow-ice drains dry. 

 When, however, a small piece of the ice is seen floating nearly 

 submerged, it looks almost of a chocolate brown colour. 



Mr. Buchanan made experiments on the melting point, and 

 amount of salt contained in salt-water ice. He came to the 

 conclusion from analyses of successive meltings and the vary- 

 ing of the melting point, that in salt-water ice " the salt is not 

 contained in the form of mechanically enclosed brine only, but 

 exists in the solid form, either as a single crystalline substance, 

 or as a mixture of ice and salt crystals." 



He thinks that by fractional melting, salt water ice might be 

 made to yield water fit to drink, although when a lump is 

 melted as a whole, the resulting water is undrinkable.t 



We crossed the Antarctic Circle on February i6th, passing 

 about six miles to the south of it. There was open water 



* Sir J. D. Hooker's collections were described by Ehrenberg. See 

 Capt. Ross's "Antarctic Voyage," Vol. I., pp. 339, 341. London, J. 

 Murraj', 1847. Ehrenberg's "Report on Deposit from Pancake Ice, 

 collected by Dr. Hooker." 



f Robert Brown, " On the Discolouration of the Arctic Seas." Quart. 

 Jour. Micro. Sci., 1865, P- 240. 



J J. Y. Buchanan, M.A., " Observations on Sea-Water Ice,"' Proc. R 

 Soc, No. 170, 1876, p. 609. 



