Intelligence and Miscellaneous Articles. 157 



if absolutely pure water would be entirely free from this weakness 

 or not, since we cannot assume that water, which has boiled for a 

 quarter of an hour or more in a glass vessel, is absolutely free from 

 minimal quantities of foreign substances, as e. (/.sodium salts, silica, 

 etc. For my own part I am rather inclined to think that absolutely 

 pure water, if it could be tested, would show an absolutely fixed 

 melting-point . . . ." In connexion with this point the author 

 remarks upon the plasticity of ice, which has been observed near the 

 melting-point, while at lower temperatures it is brittle. The author 

 shows that the irregularity in expansion is connected with the de- 

 gree of rigidity of the ice : at a sufficiently low temperature every 

 kind of ice is hard and brittle, and in this state it expands regularly 

 with increase of temperature ; the commencemert of the thawing 

 is entirely dependent upon the amount of salt, etc., present, and 

 the softening before melting is connected finally with a contraction 

 in volume : thus ice from ordinary distilled water begins to contract 

 at — o, 25 C. ; a sample containing 0*015 p. c. chlorine at — -4° 0. ; 

 and ice formed by the sudden freezing of ocean-water begins to 

 contract at —20° C. or below. As a consequence of this it is added 

 that it must be acknowledged " that the ice-masses of the glaciers 

 are liable to contraction at temperatures below their melting-point." 

 In the investigation of the chemical changes in the composition 

 of sea- water caused by freezing, the author reaches the conclusion 

 that ice formed from sea- water is not, as has generally been sup- 

 posed, essentially pure, owing its saltness to mechanically enclosed 

 brine : the result reached is the same as that obtained in a different 

 way by Dr. Buchanan of the ' Challenger/ Dr. Pettersson concludes 

 that ocean-water is divided by freezing, not into pure water and 

 a more or less concentrated solution of ordinary sea-salt, as was 

 formerly believed, but into two saliniferous parts, one liquid and 

 one solid, which are of different composition. Thus the formation 

 of sea-ice is chemically a selective process — some of the elements of 

 salt water are more fit than others to enter into the solid state by 

 freezing ; those which are rejected by the ice will preponderate in 

 the brine, and vice versa : for example, as regards the relation of 

 CI : S0 3 , the ice is richer in sulphates, the brine in chlorides. The 

 extraordinary variation both in saltness and in chemical composition 

 of every individual specimen of sea-ice and sea-brine depends upon 

 a secondary process or the metamorphosis of the ice, due to the 

 combined influences of time and variation of temperature. The 

 concluding chapter is devoted to a discussion of the latent heat of 

 fresh and salt water ; the important point brought out in it is this, 

 that the latent heat developed by the freezing of sea-water is 

 " extraordinarily inferior to that of pure water." The author adds, 

 that the freezing process, however, from a thermic point of view, 

 is not entirely concluded with the solidification of the sea-water, 

 by which it is divided into ice, solid cryohydrates, and liquid brine 

 containing dissolved salts ; for on further sinking of the temperature, 

 still unfrozen cryohydrates will be solidified and develop heat until 



