94 THE FAIRY-LAND OF SCIENCE. 
that it is " white as snow." Some of these crystals 
are simply flat slabs with six sides, others are stars 
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-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 
turning into water, and the bright spot in the middle 
is a bubble of empty space, left because the watery 
flower does not fill up as much room as the ice of the 
crystal star did. 
And this leads us to notice that ice always takes 
