POLAR ICE. — ABSTRACT OF OBSERA^ATIONS. 321 



water or sea-water, is, excepting such parts above 

 water as have been recently washed by the sea du- 

 ring frost, perfectly free from salt. 



That porous light ice, and even bay-ice, when 

 well drained in a mild temperature, and washed 

 with fresh water, generally produce potable water, 

 though not always entirely free from salt. 



VII. Quantity of ice. — That an equilibrium be- 

 tween the quantity of new ice produced and of old 

 ice destroyed, is so well preserved, that the abso- 

 lute quantity of ice in the polar seas is always nearly 

 the same ; the south-westerly drift of the ice renews 

 the front exposed to the sea, and prevents the in- 

 roads of the swell, while the general action of the 

 waves of the ocean, and the influence of a compa- 

 ratively mild temperature, prevent the ice fi-om 

 spreading over the Atlantic. 



That when the quantity of ice in any place is en- 

 larged or diminished, the variation is only tempo- 

 rary and partial ; the usual equality being general- 

 ly restored in the course of a few years by the re- 

 versed operation of the very causes which produced 

 the inequality. 



VIII. Quantity of ice greate7^ in the southern 

 than in the northern hemisphere. — That there ap- 

 pears to exist a remarkable difference between the 

 two hemispheres with regard to the extent from 

 the Poles occupied by the ice ; the ice which en- 



VOL. I. X 



