90 THE FAIRY-LAND OF SCIENCE. 
with six rods or spikes springing from the centre, 
others with six spikes each formed like a delicate 
fern. No less than a thousand different forms of 
delicate crystals have been found among snow- 
Fig. 22. 
Snow-crystals. 
flakes, but though there is such a great variety, yet 
they are all built on the six-sided and six-pointed 
plan, and are all rendered dazzlingly white by the 
reflection of the light from the faces of the crystals and 
the tiny air-bubbles built up within them. This, you 
see, is why, when the snow melts, you have only a little 
dirty water in your hand ; the crystals are gone and 
there are no more air-bubbles held prisoners to act as 
looking-glasses to the light. Hoar-frost is also made 
up of tiny water-crystals, and is nothing more than 
frozen dew hanging on the blades of grass and from 
the trees. 
But how about ice ? Here, you will say, is frozen 
water, and yet we see no crystals, only a clear trans- 
parent mass. Here, again, Dr. Tyndall helps us. He 
says (and as I have proved it true, so may you for 
yourselves, if you will) that if you take a magnifying 
glass, and look down on the surface of ice on a sunny 
day, you will see a number of dark, six-sided stars, 
looking like flattened flowers, and in the centre of each 
a bright spot. These flowers, which are seen when 
the ice is melting, are our old friends the crystal stars 
