VEGA-EXPEDITIONEN S VETENSKAPLIGA ARBETEN. 



287 



chance to walk over a plain of newly formed ice before any 

 snow has fallen, you will be astonished to find every footstep 

 impressed in the mäss just as in melting snow. If unacquaint- 

 ed with the fact, you will in vain try to understand, how 

 the solid ice can be in a melting condition at a temperature 

 of — 40'' C or still more» [Weyprechtj. The specimen of 

 ice examined in series VI of the following chapter and repre- 

 sented in curve VI of plate 21 claims to be a representative 

 of this kind of polar ice. It is formed by sudden freezing of 

 ocean water of ordinary saltness from the Siberian sea and 

 itself contains 0.649 p. c. of chlorine, according to the titration. 



The plastic properties of such ice, described by Wey- 

 precht, will be found to correspond to a premature contrac- 

 tion of volume, which begins already at — 20" C. The prece- 

 ding diminution of expansion dates from a stage of tempera- 

 ture far beyond — 20° C, the limit of my investigations. 



We may now understand, why people of the trade are sa 

 very particular about the locality, from which the ice of com- 

 merce is taken. Everbody knows, that ice from the open sea 

 would not do for the märket, hut J dåre say, that everybody 

 does not know the reason why. Somebody may hint, that 

 ice from salt water must be disagreeable to the taste, but this 

 is far from being always the case. The most refined palate 

 will fail to detect the slight saltness of olä sea-ice. At Cloven 

 cliff, northwest of Spitzbergen, I have collected blocks of ice 

 from the polar drift-current, which contained less than one 

 fourth of the amount of chlorides, which is found in the 

 drinking water of Stockholm. It is solely on account of the 

 physical properties accompanying this diminutive percentage 

 of salt, that sea-ice is rejected by the trade. Only the almost 

 chemically pure ice, produced by freezing of inland lakes,, 

 deficient in chlorides etc. will bear transportation without 

 crumbling and conserve the glass-like hardness and trans- 

 parency, which is an indispensable condition of ice as an ar- 

 tide of consumption and of luxur3^ 



Any physicist, familiar with the use of Bunsen's ice 

 calorimeter, will also, like the author, be familiar with the 

 capriciousness of this instrument. Bunsen prescribes, that 

 the calorimeter should be placed in a big vessel filled with 

 cntirely pure snow. Although I have bad abundant quantities 

 of the purest snow at my disposal, I do not hesitate to de- 

 clare, having tried during a Avhole winter to obtain reliable 

 results with the original arrangement of the inventor, that 



