POLAR ICE. — DIFFERENT KINDS. 229 



14. Open ice, or sailing-ice, is where the pieces 

 are so separate as to admit of a ship sailing conve- 

 niently among them. 



15. Heavy and light are terms attached to ice, 

 distinguishable of its thickness ; heavy ice having a 

 considerable depth in the water, and light ice very 

 little ; the former being dangerous to shipping, and 

 the latter not. Bay-ice may be said to extend 

 from the first pellicle of ice, up to a foot in thick- 

 ness ; light ice from a foot to a yard in thickness ; 

 and heavy ice from about a yard upwards. 



16. Land-ice consists of drift-ice attached to the 

 shore ; or drift-ice, which, by being covered with 

 mud or gravel, appears to have recently been in con- 

 tact with the shore ; or the flat ice, resting on the 

 land, not having the appearance or elevation of ice- 

 bergs. 



17- A bight is a bay in the outline of the ice. 

 18. A lane, or vein, is a narrow channel of water 

 in packs, or other large collections of ice. 



When the sea freezes, the greatest part of the 

 salt it contains is deposited, and the fi'ozen mass, 

 however spongy, probably contains no salt, but what 

 is natural to the sea-water filling its pores. Hence 

 the generality of ice, when dissolved, affords fresh 

 water. As, however, the ice frozen altogether from 

 sea-water does not appear so solid and transparent 

 as that procured from snow or rain water, the whale- 



