VEGA-EXPEDITIONENS VETENSKAPLIGA ARBETEN. 



319 



temperatiire [Ti = — 0°. . . C] of nearly pure ice. Water can 

 not absorh or äevelop the same quaniity of latent heat at tivo dif- 

 ferent temperatiires. Besides, the presence of salt ia freezing 

 water has the property of diminishing its latent heat, at least 

 if the solidification, as always in nature, takes place a few 

 degrees below zero. ^ 2 or 3 p.c. of salt dissolved in pure 

 water has the same depressing infiuence on its latent heat 

 and likewise on its freezhig temperature as an increase of 

 pressure amounting to some hundreds of atmospheres. 



From these premises we can draw the following conclu- 

 sions: 



1. In the imagined example a complete cycle - of heat 

 takes place. The qnantity of ice {^= I kgrm), which was sup- 

 posed to melt in the warm water of the Gulf-stream, is also 

 supposed to return to its original point of depart, in its initial 

 state of pure or nearly pure ice. 



2. Meanwhile it undergoes the following transformations: 



it melts at — 0° . . [absolute temperature T = 273°]. 

 Thereby it absorbs the latent. heat Q ^ 



it mingles with the surrounding ocean- 

 water and thereby absorbs heat, qi å^ 



of sea-water. But in those parts ot the ocean, where a real melting of sea- 

 ice takes place. the temperature never sinks so low. Tliat part of the ice,^ 

 which is first liquefied, forms a stratum of fresh water around the ice-floe 

 wherein the rest of the ice liquefies at its ordinary melting point. Verv 

 often the fresh or diliited sea-water in the vicinity of melting ice is found 

 to be of surprisingly high temperature. The lowest temperature observed 

 on the bank of New-Foundland during 5 years was — 0°.9 R, the mean tem- 

 perature was +3°. 01 R. [Proceedings of R. S. 1869. M 3.] On the other 

 hand the temperature of freezing sea-water has never been found to be 

 liigher than tlie ordinary freezing point of the water. See the observations 

 of Scoresby 1810 — 1817 and those of the Vega-expedition in Sept. 1878 a. O. 



* I consider this reservation to be necessary, because the temperatures 

 of the freezing experiments, enumerated in table 2 of this chapter, do 

 not exceed the limits — 9° C and — 8" O. Having no experiments to rely 

 upon at lower or higher temperatures, I do not wish to extend the rule 

 beyond the dominions of experience. 



- In order to prepare the application of Carnofs theorem to the ex- 

 ample in question, I denote the quantities of heat absorbed or developed 

 by the water at every one of these secondary changes by >q» and in the 

 case of ice by »r». The corresponding absolute temperatures are T, Ti^ 

 T2 . . . T', Ti Thus we may form the quotients Hi , R;? . . . Il , Ii etc. . . 



^ Ti' Ti Ti'' Ti' 



[»die Aequivalenzwerthe> of Clausius]. 



