640 PHYSICAL PROPERTIES OF ICE, 



4. Ice Observations. By Dr. Walker, daring the Voyage of 

 the " Fox." (From the Journal of the Royal Dublin Society, 

 Jan. 1860.) 



My attention was directed to the analysis of ice, and the changes 

 produced in sea-water when freezing, by the various and contra- 

 dictory opinions held by different authorities. Sir Chai'les Lyell, 

 in his " Principles of Geology," p. 96^ states that sea- water ice is 

 freshf having lost its salt by the decomposing process of freezing. 

 Dr. Sutherland, in his " Journal of Penny's Voyage," says that 

 sea-water ice is salt, containing about a quarter part of the salt 

 of the original water, the proportion depending upon the tempera- 

 ture ; it being very probable that the lower the temperature is the 

 more salt the ice will contain. At variance with both of these. 

 Dr. Kane asserts in his '' Arctic Expedition," pp. 377, 385, 392, 

 that, although at some temperatures and at some small thicknesses 

 the ice mai/ be salt, yet, " if the cold be sufficiently intense, inde- 

 " pendent of percolation, solar heat, depending position, or even 

 *' depth of ice, there will be formed from salt water afresh, pure, 

 '' and drinkable elementr Baron Wrangell ("Le Voyage au 

 Nord de la Siberie ") mentions that the salt left hj evaporation on 

 the surface of the ice is mixed with the snow that falls upon it, 

 and is eaten as salt with food, though bitter and aperient. 



Five different sets of observations were carried out during the 

 winters of 1857-8 as we drifted down Baffin's Bay, Davis' Strait. 



1st. To observe the changes in specific gravity of sea-water ice 

 formed under different degrees of cold. 



2nd. Forming fresh water from salt (or sea) water, by freezing 

 the latter, and thawing and re-freezing the ice thus formed, 

 continued one, two, or three times, as necessary, at different 

 temperatures. 



3rd. Converse of last, forming brine from sea-water by freezing 

 at different temperatures, and re-freezing the residue. 



4th. Specific gravity, &c., of saline efflorescence at different 

 temperatures expressed from sea-water ice in its early process of 

 formation. 



5th. Specific gravity of ordinary ice of winter formation at 

 close of winter, taking specimens at different depths. 



On the 7th of September 1857, we were frozen in whilst 

 endeavouring to pass through Melville Bay, and until the month 

 of April 1858 our ship was immoveably fixed in the ice. During 

 all the intervening time I have Avatched and tested the growth 

 and condition of the ice formed, taking advantage of all oppor- 

 tunities which offered, and filling up every blank, as far as possible^ 

 by artificial means. An abstract of the changes produced are 

 here given, with tables of the observations. 



When the temperature of the water and air falls below 28° '5, 

 sea-water exposed will in a short time be covered v/ith a thin and 

 almost pellucid pellicle of ice, of a very plastic nature, allowing of 

 a great amount of bending, curving, and such like accommodations 

 to external circumstances. In proportion to the temperature, 

 this covering becomes thicker, and presents a vertically striated 



