POLAR-ICE. — EXPERIMENTS. 235 



mass Hoating in the sea, there must be at least 

 8 feet below. A cubic inch of compact ice weighs 

 231.5 grains, and a cubic inch of Greenland sea- 

 water at a freezing temperature, specific gravity 

 (temp. 60°) 1.0264, weighs 259.58 grains ; the 

 weight of ice being to the weight of sea- water as 

 8 to 8.97, or 8 to 9 nearly. 



Water, under usual circumstances, is known to 

 contain a large quantity of air, amounting to per- 

 haps i^^ih or ^ th of its bulk, which air, it is sup- 

 posed is chiefly disengaged when the fluid is boiled. 

 It would, however, appear, that the whole of the 

 air contained in water is by no means disengaged 

 even when boiling, as water that has been boiled 

 and then frozen iii vacuo, does not form a trans- 

 parent ice. The following experiment on the dis- 

 engagement of air from water during the freezing, 

 intended for observing the phenomena more minute- 

 ly than can be seen on the great scale on which na- 

 ture, in the expanse of the ocean, operates, was 

 made near Spitzbergen. 



Into a 4 oz. clear glass-phial, I poured 2 oz. of 

 ice-water, and placing it upon the fire in a salt-wa- 

 water bath, soon brought it to the boiling point. 

 Being removed to the front of a brisk fire, a strong 

 ebullition commenced, which having continued for 

 some time, accompanied with a copious disengage- 

 ment of steam, the phial was suddenly corked and 

 inverted. It was then exposed to a temperature of 



