Chemical and Physical Notes 



125 



they were not more than I kilometre distant from each other. Considering 

 the temperatures at a height of i m., there is a difference of 6'5 between 

 the land and the ice. The difference of vapour tension, o - 2 mm., is 

 insignificant, and shows that substantially the air is the same. The dew- 



TABLE XXII. Temperature Observations at Equal Altitudes on the 

 Morteratsch Glacier, and on the Mountain West of it. 



point in both cases is several degrees below o, so that, on the air coming 

 in contact with the ice, there would be evaporation from the latter. The 

 evaporating power of the air may be represented by the difference between 

 the tension of saturation and the actual vapour tension. It is very great 

 on land, being 1075 mrn - at '6'53 C., and it would rapidly evaporate 

 water having that temperature. On coming in contact, however, with 



