THE TWO GREAT SCULPTORS. 115 
the sea, it falls down to form new land. But what 
becomes of the dissolved chalk and other substances ? 
We have seen that a great deal of it is used by river 
and sea animals to build their shells and skeletons, 
and some of it is left on the surface of the ground by 
springs when the water evaporates. It is this car- 
bonate of lime which forms a hard crust over any- 
thing upon which it may happen to be deposited, and 
then these things are called " petrified." 
But it is in the caves and hollows of the earth 
that this dissolved matter is built up into the most 
beautiful forms. If you have ever been to Buxton in 
Derbyshire, you will probably have visited a cavern 
called Poole's Cavern, not far from there, which when 
you enter it looks as if it were built up entirely 
of rods of beautiful transparent white glass, hanging 
from the ceiling, from the walls, or rising up from the 
floor. In this cavern, and many others like it,* water 
comes dripping through the roof, and as it falls 
slowly drop by drop it leaves behind a little of the 
carbonate of lime it has brought out of the rocks. 
This carbonate of lime forms itself into a thin, white 
film on the roof, often making a complete circle, and 
then, as the water drips from it day by day, it goes on 
growing and growing till it forms a long needle-shaped 
or tube-shaped rod. hanging like an icicle. These rods 
are called stalactites, and they are so beautiful, as their 
minute crystals glisten when a light is taken into the 
cavern, that one of them near Tenby is called the 
" Fairy Chamber." Meanwhile, the water which drips 
on to the floor also leaves some carbonate of lime 
* See the picture at the head of the lecture. 
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