CRUISE OF STEAMER COR WIN IN THE ARCTIC OCEAN. 1 29 



it was only by most carefully noting the movements of the darkened patches that he was enabled 

 to say positively that the reported land did not exist. 



In regard to the purification of sea-water by freezing, Dr. Kane says that the cold, if intense 

 enough, will, by its unaided action, independent of all other considerations, produce from salt water 

 a fresh, pure, and drinkable element, but that ice formed in this way, when exposed to a high tem- 

 perature, becomes infiltrated with saline matter by forces allied to endosmosis. He discovered 

 that the floes which formed in midwinter at a temperature of 30° were still fresh and pure, while 

 the floes of slower growth or those formed early and late in the season when the temperature was 

 higher were distinctly saline. Ice which two months before he had eaten with pleasure was soon 

 so salt that the very snow which covered it was no longer drinkable. Ice formed with the tem- 

 perature 20° or 30° below zero was of almost flinty hardness, and when tested with nitrate of 

 silver gave no trace of salt. Sir Charles Lyell states that sea- water ice is fresh, having lost its salt 

 by the decomposing process of freezing. Dr. Sutherland, in his "Journal of Parry's Voyage," says 

 that sea- water ice is salt, containing about one quarter part of the salt of the original water, the pro- 

 portion depending upon the temperature. It is very probable that the lower the temperature the 

 more salt the ice will contain. Parry himself, in his account of his attempt to reach the North 

 Pole by boats, says : " I was desirous, also, of ascertaining whether any part of the real sea-ice was 

 so entirely fresh when melted as to be drank without injury or inconvenience. For this purpose," 

 he says, " we cut a block of ice from a large hummock about 10 feet high above the sea, and having 

 broken, pounded, and melted it without any previous washing, we found it, both by the hydrome- 

 ter and the chemical tests — nitrate of silver — more free from salt than any which we had in our 

 tanks aud which was procured from Hammerfest." He considered this satisfactory, because in the 

 autumn the pools of water met with upon the ice generally become very brackish^ in consequence 

 of the sea-water being drawn up into them by capillary action, as the ice becomes more rotted 

 and porous; and he might, therefore, have to depend chiefly upon melted snow for their daily sup- 

 ply. During the two cruises of the Corwin in the Arctic seas, I tried the sea-ice many times, 

 and to the taste (we had no meaus of applying delicate chemical tests) the clear blue ice, although 

 taken from below the surface of the sea, appeared perfectly fresh. The ice melted, and, standing 

 in pools on the surface of the floes, was also found to be fresh in most instances, and we several 

 times filled our water-tanks from them with good drinkable water. Experiments have shown 

 that successive freezing and thawing of sea-water tends to reduce the percentage of impurities which 

 it contains ; but I am not aware of these having been carried far enough to render it absolutely 

 pure. After several attempts on board the Fox, the specific gravity of sea-water was reduced, by 

 repeated freezing and thawing, to five ten thousandths (.0005). Wrangel says the salt left by 

 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. Dr. Walker, who accompanied McClintock in the 

 Fox, and who made a careful aud systematic set of ice observations in Baffin's Bay and Davis Strait 

 during the winter of lS57-'58, noticed the saltuess of the crystals on the ice, but shows that it 

 could not be due to evaporation, as supposed by Wrangel. Evaporation is less in proportion to the 

 cold, while the amount of salt crystals increase in the same proportion. Dr. Walker says when the 

 temperature of the water aud air fall below 28°.3, sea-water exposed will in a short time be cov- 

 ered with a thin and almost pellucid pellicle of ice of a very plastic nature, allowing of a great 

 amount of bending, curling, and such like accommodations to external circumstances. In propor. 

 tion to the increased temperature this covering becomes thicker, and presents a vertically striated 

 appearance, identical with that of sal ammoniac, gradually disappearing as the mass thickens and 

 gets more compact; still, the lowest portion or that most recently formed, always presents this 

 aspect. When this pellicle or covering becomes of the thickness of a quarter of an inch or more, 

 small white crystals appear on the surface, at first sparse and widely separated, but gradually form- 

 ing into tufts and ultimately covering the whole surface. Mr. Nelson, in his general notes on the 

 climate and meteorology of Saiut Michael's, says of the formation of ice : 



Sludge ice forms in the bays -with the temperature at 30°. 5 F., and in addition the whole surface of the sea, if calm, 



appears covered with large oily-looking patches, which slowly increase in area, and as the water reaches 30° the 



Bludge begins to unite. In the oily-appearing spots the water, on close view, has a milky sh;ide, aud is seen to he full 



of extremely fragile lamina; of ice, floating with their edges vertical. These plates, when broken and ground up. 



S. Ex. 204 17 



