Andy Reinert, age 14, of Glendale, Ariz., for his question:

WHICH HANGS DOWN FROM THE CEILING, THE STALACTITE OR STALAGMITE?

Stalactites and stalagmites are mineral formations frequently found in caves.

The stalactite is the icicle shaped mass of accumulated calcium carbonate hanging down from the ceiling or sides of a limestone cave. It is formed by mineral precipitation from ground water that has seeped, very slowly, through the roof of the cavern.

Water circulating through the ground above a cavern picks up calcium bicarbonate as it percolates through the limestone. When the water trickles through the ground to the roof of a cavern, it tends to cling to the roof in droplets. As the droplets lose some of their water and carbon dioxide, calcium carbonate is precipitated and forms a deposit.

As more water seeps through the roof of the cavern, the precipitation of calcium carbonate continues and the deposits grow in length and width, forming stalactites. These are often of enormous size and beautiful shape.

To remember it is the stalactite hanging down from the ceiling, think of the last part of the word: "tite." Remember that it is the stalactite that holds on "tight."

Some of the water seepage falls to the floor and accumulates into masses resembling inverted stalactites. These deposits, growing upward form the floor, are called stalagmites.