THE PHYSICS OF ICE. 



401 



lines are portions which have become liquid. We have seen that freez- 

 ing is a process in which water expands in volume. This implies change 

 in its molecular structure, or that the molecules assume new positions. 

 Perhaps the wonderful movement of particles around the poles of a 

 magnet, illustrated by Fig. 2, may suggest the nature of the interior 

 movements which occur in the crystallization of water. Certain it is 

 that the molecules recede from each other and occupy more space than 

 when they lay compacted in the liquid condition. 



Magnetic Curves. 



Water expands, in freezing, with a force that is practically irre- 

 sistible, its increase in volume being about ten per cent. Flasks of 

 copper and iron are broken by it. Rocks are split asunder and disin- 

 tegrated, and from this cause the freezing of water plays an important 

 part in geological changes. A bomb-shell filled with water and closed 

 by an iron stopper was exposed to frost ; in a little time the stopper 



Experiments, showing Force op Expansion. 



was driven out to a distance of several hundred feet, and a mass of 

 ice protruded. In another case the shell burst, and a sheet of ice ex- 

 panded around the crevice. These tremendous mechanical effects are 

 shown in Fig. 3. In these and similar cases the water may not have 



VOL. T.— 26 



