Sandra Kryzan, age 10, of Guths Station, Penna., for her question:

What are stalactites and stalagmites?

Vie find these stony icicles in damp, cool caves   but before we go hunting for theme here is a word of warning. Spelunking, or cave exploring, is a very dangerous hobby, even when we have an expert along. Certainly none of Andy's young friends would be silly enough to try such an adventure on his or her own. There are plenty of safe eaves across the country fitted with walks and lights. We can also find guides to point out the beauties and tell us how these wonders came to be. So let's not take chances with our precious lives by searching for caves of our own.

As we walk through the cool damp caves we see handsome stonework on all sides. Graceful scrollwork festoons the walls. Here and there are furls of folded drapery like flowing curtains made of stone. Those stony icicles hanging from the ceiling are stalactites. Those stony spikes rising up from the ground are stalagmites. Usually there is a stalagmite poking up from the ground right under a dripping stalactite. Sometimes the two meet to form a stony pillar from floor to ceiling.

All this beautiful stone masonry was made by running water. Listen anal you will hear the drip drip of water in the cave. The air is cool atd clammy with evaporating moisture. Chances are, our cave is a hollow, deep do ,m in a limestone hill. All these things work together to form the store embroidery which decorates the walls, floor and ceiling of our cave,

The running water, of course, comes tumbling down as rain. When the soil is soft, it sinks down and down, trickling through the cracks and seeping into the pores of rocks such as limestones* And water laps at the rocks with greedy little tongues. Rocks are made of chemicals and some of these chemicals dissolve readily in the seeping water. In limestone, the chemical dissolved is calcite,

Water seeping through the limestone hill becomes loaded with calcite. Much of the limestone is dissolved and soon we have a hole deep in the hill. More water trickles down and seeps through the sides of the hole. It gets bigger and bigger until it becomes a cave. And still the water drip drips through the walls and through the ceiling,

In the a1r of the cave, the dripping water begins t o evaporate. The liquid water turns to water vapor, which is a gas. When this happens, it must leave its dissolved chemicals behind. Bit by bit, the dripping crack in the ceiling builds up a deposit of calcite$ the same mineral which was dissolved from the limestone hill. The pile of calcium grows into a stalactite. Water drips from its tip onto the ground below. This water also evaporates. This time the load of dissolved calcite builds up a stalagmite,