GREENLAND OR POLAR ICE. 'g^^ 



ships are sometimes so caught by a change of 

 wind, that the ice cannot be cleared on either 

 tack ; and in some cases, a total loss has been the 

 consequence. 



Comparison of Ice frozen from Sejci-Water and 

 Rain-Water. 



When the sea freezes, the greatest part of the 

 salt it contains is deposited, and the frozen spongy 

 mass probably contains no salt, but what is natu- 

 ral to the sea- water filling its pores. Hence, the 

 generality of ice affords fresh-water, when dis- 

 solved. As, however, the ice frozen from sea^ 

 water does not appear so solid and transparent as 

 that procured from snow or rain-water, sailors 

 distinguish it into two kinds, accordingly as it 

 seems to have been formed from one or the other. 



Ice frozen from Sea- Water, 



What is considered as salt-water ice, is porous, 

 white, and in a great measure opaque, (except 

 when in very thin pieces), yet transmits the 

 rays of light with a greenish shade. It is softer, 

 and swims lighter than fresh-water ice, and when 

 dissolved, produces water sometimes perfectly 

 fresh, and sometimes saltish , this depends in a 

 great measure on the situation from whence it is 

 taken : such parts as are raised above the surface 

 of the sea in the form of hummocks, appear to gain 



s4 



