liquid into fine dust; sometimes it breaks it into little pieces and
fills them with bubbles. At another time the steam is not so strong and
only pushes the stuff out gently over the crater's edge. Many different
minerals are found in these rocks--iron, copper, lead, mica, zinc,
sulphur. Some pieces are beautiful in color--blue, green, red, yellow.
Precious stones have sometimes been found--garnets, topaz, quartz,
tourmaline, lapis lazuli. But most of the stone is dull black or brown
or gray.

All this heavy matter drops close to the mountain. And on calm days the
ashes, also, fall near at home. Indeed, the volcano has built up its own
mountain. But a heavy wind often carries the fine dust for hundreds of
miles. Once it was blown as far as Constantinople and it darkened the
sun and frightened people there. Some of the ashes fall into the sea.
For years the currents carry them about from shore to shore. At last
they settle to the bottom and make clay or sand or mud. The material
lies there for thousands of years and is hard packed into a soft fine
grained rock, called tufa. The city of Naples to-day is built of such
stone that once lay under the sea. An earthquake long ago lifted the
ocean bottom and turned it into dry land. Now men live upon it and cut
streets in it and grow crops on it.

So for many miles about, Vesuvius has been making earth. Her ashes lie
hundreds of feet deep. Men dig wells and still find only material that
has been thrown out of the volcano. When this matter grows old and lies
under the sun and rain it turns to good soil. The acids of water and air
and plants eat into it. Rain wears it away. Plant roots crack the rocks
open. The top layer becomes powdered and rotted and mixed with vegetable
loam and is fertile soil. So the country all around the volcano is a
rich garden. Tomatoes, melons, grapes, olives, figs, cover the land.