POLAR ICE. 435 
They consist of a clear, compact, and solid ice, which has 
the fine green tint, verging to blue, which ice or water, when 
very pure and of a sufficient depth, always assumes. From 
the cavities of these icebergs the crews of the northern wha- 
lers are accustomed, by means of a hose, or flexible tube of 
canvass, to fill their casks easily with the finest and softest 
water. Of the same species of ice, the fragments which are 
picked up as they float on the surface of the ocean yield the 
adventurous navin-atoi the most refreshins: beveraa^e. 
It was long disputed among the learned, whether the waters 
of the ocean are capable of being congealed; and many fri- 
volous and absurd arguments, of course, were advanced to 
prove the impossibility of the fact. But the question is now 
completely resolved ; and the freezing of sea-water is esta- 
blished both by observation and experiment. The product, 
however, is an imperfect sort of ice, easily distinguishable 
from the result of a regular crystalization ; it is porous, in- 
compact, and imperfectly diaphanous. It consists of spicular 
shoots, or thin flakes, which detain within their interstices the 
strongest brine ; and its granular spongy texture has, in fact, 
the appearance of congealed syrup, or what the confectioners 
call water-ice. This saline ice can, therefore, never yield 
pure water ; yet if the strong brine imprisoned in it be first 
suffered to drain off slowly, the loose mass that remains will 
melt into a brackish liquid, which in some cases may be 
deemed potable. 
To congeal sea-water of the ordinary saltness, or contain- 
ing nearly the thirtieth part of its weight of saline matter, it 
requires not an extreme cold ; this process takes effect about 
the 27th degree of Fahrenheit's scale, or only five degrees 
below the freezing point of fresh water. Within the arctic 
circle, therefore, the surface of the ocean being never much 
warmer, is, in the decline of the summer, soon cooled do^vn 
to the limit at which congelation commences. About the end 
of July, or the beginning of August, a sheet of ice, perhaps 
an inch thick, is formed in the space of a single night. The 
frost now maintains ascendancy, and shoots its increasing en- 
ergy in all directions, till it has covered the whole extent of 
those seas with a solid vault to the depth of several feet. But, 
on the return of spring, the penetrating rays of the sun gra- 
dually melt or soften that icy floor, and render its substance 
friable and easily disrupted. The first strong wind, creating 
a swell in the ocean, then breaks up the vast continent into 
large fields, which are afterward shivered into fragments by 
