And so, with a hoe, the man scraped away two or three inches of loose gravel, and there they saw hot sand boiling and bubbling just like a hot pudding. A cloud of black smoke rose from the boiling sand, and a very bad odor made Molly and May cover their noses with their handkerchiefs. May tried to pick up a small stone near her feet to carry home with her, but it was so hot she dropped it very quickly.
"Oh! oh!" cried May. "Is the world going to burn up?"
"Oh, dear! Oh, dear! Where are we? Is this a volcano?" cried Molly.
"That's just what it is," said their guide. "This is the volcano of Solfatara, and we are on the top of it. This big round field, or basin, is the crater of the volcano. It boiled over many years ago, then it cooled off. Now it is getting hotter again, but it is not nearly so hot as Vesuvius over yonder."
"Oh, it's hot enough!" exclaimed May. "I don't like volcanoes. I'm not having a nice time. I want to go back to the carriage. What if the volcano should boil over while we are on it?"
"It will not," said the guide. "It is not hot enough yet. But something may happen some time. I hope I shall not be here when it does. Now let us take a look into those cracks where the smoke and gas are pouring out. I will swing my torch over one of the cracks and you shall see something wonderful. Now watch!"
In a moment hot flames shot several feet into the air, and clouds of black smoke surrounded the little party.
"Oh! oh!" cried May. "Is the world going to burn up?"
"No, indeed!" said her father. "Don't be frightened. That was only a little gas which the guide set on fire with his torch, just as mother lights her gas stove at home. There is a pretty big furnace underneath us, and it sends off a good deal of gas. It is the gas that smells so bad and makes us cover our noses."