On Ice and Brines 149 



heat of this mixture from the heat liberated in the calori- 

 meter during freezing, and assuming that the whole mass had 

 solidified, Pettersson's results give the mean latent heat of 

 this sea-water as 52'!. Calculating the apparent latent heat 

 on the assumption that 70 per cent, of the mass solidifies into 

 pure ice and that 30 per cent, remains liquid, .we get the 

 number 51*5. On all grounds therefore we must conclude 

 that pure ice is the primary product in freezing sea-water and 

 saline solutions of moderate concentration. 



The plasticity of ice and the motion of glaciers receive a 

 simple and natural explanation when we see, as in Table IX, 

 that, if the water from which this ice is produced contains no 

 more than 7 parts of chlorine per million, it will, in the process 

 of thawing, when the temperature has risen to o'O7 C., 

 consist to the extent of I per cent, of its mass of liquid brine 

 or water. The water considered in Table IX is certainly 

 not less free from foreign ingredients than rain or snow. It 

 follows, therefore, that a glacier, in a climate where the 

 temperature is for the greater part of the year above o C., 

 mut have a tendency to flow, owing to the power of saline 

 solutions to deposit ice and to dissolve it at temperatures 

 below o C. 



The verification of thermometers by comparison with the 

 air thermometer is always troublesome. It results from the 

 above investigations that, if the temperature at which ice 

 melts in solutions of a salt, such as chloride of calcium of 

 different degrees of concentration, were once and for all 

 carefully determined by means of a standard air thermometer, 

 a thermometer could be indirectly but satisfactorily compared 

 with the air thermometer at temperatures below o C. by 

 immersing it in a mixture of ice and chloride of calcium 

 solution, and taking a series of readings of the thermometer 

 and samples of the brine simultaneously. By determining 

 the chlorine in the samples the concentration of the brine is 

 ascertained, and the comparison with the standard effected. 



Freezing Mixtures. The results obtained in examining 

 the melting-point of ice in saline solutions afford data for 

 mixing freezing-baths of any degree of cooling power. With 



