IV.] SNOW AND ICE, 57 



instance, a given bulk of water, measured at that tempera- 

 ture at which its relative weight is greatest, be found to 

 weigh i,ooo pounds, an equal bulk of ice will weigh only 

 916 pounds. Hence ice floats readily on water, and floats 

 with only about one-tenth of its volume above the surface. 

 This may be seen by dropping a lump of ice into a tumbler 

 of water, and observing how much is exposed, and how 

 much buried in the water (Fig. 14.) Sea-water is denser, 

 or heavier bulk for bulk, than fresh water ; and therefore a 

 mass of ice floats higher in the ocean, about one-ninth of its 

 volume being then exposed. Hence, in those huge masses 

 of ice which are frequently seen floating in the sea and are 

 known as icebergs, the bulk of ice which 

 is submerged is about eight times as 

 great as that above water. But it must 

 be remembered that the proportion of 

 the submerged to the exposed part of 

 the total height of the berg will be 

 affected by the shape of the mass ; and 

 probably, in many cases, the shape of Fig. 14.— ice \.\ water 

 the berg is such as to cause it to sink 

 to a very much smaller proportion of its total height beneath 

 the surface than that represented in Fig. 14. 



It must not be supposed that the compact hard substance 

 which is produced by the freezing or consolidation of 

 water is a solid body without structure, like a piece of glass. 

 Look at a bedroom window on a frosty morning, and you 

 will probably find that some of the moisture present in the 

 room has condensed upon the glass and frozen into solid 

 ice ; but you will see at once that this ice, instead of 

 spreading itself uniformly over the surface, has shot out in 

 'definite directions, producing beautiful branching forms, not 

 unlike the graceful fronds of a fern. The ice has, in fact, 



