“At last we reached a broad, hot piece of ground. Here were smoking holes. The night before I had looked at them with a telescope from the foot of the mountain. I had seen red rivers flowing from them. Now they were empty. Last night’s lava lay on the slope, cooled and black. I was standing on it. My feet grew hot. I had to keep moving. The air I breathed was warm and smelled like that of an iron foundry. I pushed my pole into a crack in the rock. The wood caught fire. I was standing on a thin crust. What was below? I broke out a piece of the hard lava. A red spot glared up at me. Under the crust red-hot lava was still flowing. I knew that it would be several years before it would be perfectly cool.” So for three centuries people have watched Vesuvius at work. But she is much older than that--thousands of years older--older than any city or country or people in the world. In all that time she has poured out millions of tons of matter--lava, huge glassy boulders, little pebbles of pumice stone, long shining hairs, fine dust or ashes. All these things are different forms of melted rock. Sometimes the steam blows the 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.