A DROP OF WATER. 
93 
Picture to yourselves that all the particles of those 
substances which form crystals have poles like our 
magnets, or your needles, then you can imagine that 
when the heat which held them apart is withdrawn and 
the particles come very near together, they will ar- 
range themselves according to the attraction of their 
poles and so build up regular and beautiful patterns. 
So, if we could travel up to the clouds where this 
fairy power of crystallization is at work, we should 
FIG. 23. Snow-crystals. 
find the particles of water-vapour in a freezing atmos- 
phere being built up into minute solid crystals of 
snow. If you go out after a snow-shower and search 
carefully, you will see that the snow-flakes are not 
mere lumps of frozen water, but beautiful six-pointed 
crystal stars, so white and pure that when we want to 
speak of anything being spotlessly white, you say 
