Mrs. Gray and the three children stood gazing at this phenomenon for some time in silence. At length Rollo said, "What an astonishing blast that is, to be coming up out of the earth, day and night, continually and forever!"
"The ground is very hot all about here," said the boy. "See!"
So saying, he pointed to the old man, who was at work not far from the mouth of the cave, digging into the ground a little way with a sharp hoe. He dug down a few inches, and then took up a hoe full of the earth, and held it out to Rollo to try it with his fingers, that he might feel how hot it was. Rollo put his fingers upon the earth, but he could not hold them there an instant.
It seemed to Mrs. Gray that it must be dangerous to remain long in such a place; and so she prepared to move away, and Rollo and Josie, as they had now seen all that there was to be seen at this place, followed her. They went on by the road, round to another part of the crater, where there was some sort of manufactory of alum. The alum was made from the saline earth which was found there, and the evaporating basins used in the process, instead of being placed over a fire, were simply set in the ground, so that the process of evaporation was carried on by the natural heat of the soil.
After leaving this place, the party followed the circuit of the road still farther, until at last it brought them back to the place where they had entered the crater; and here, after paying the old man who had conducted them around, they passed out through the gate, and went down the lane to their carriage.
"Now to the amphitheatre," said Rollo, addressing the coachman.
So they all got into the carriage again, and the coachman drove down the lane; and after going back towards the town a little way, and making various turns, he stopped at last before a great wooden gate. A man in a certain uniform appeared at the gate and unlocked it, and they all went in.
They saw before them the walls of an immense ruin. The wall was of a curved form, and there were vast openings in it, like arches, below. The man in uniform, who was the custodian, as they call him, of the ruin, led the way along a path into one of these arches, and thence ascended a massive flight of old stone steps, to a place which commanded a view of the interior.
They saw that the amphitheatre was of an oval form, and was built with seats rising one above another, all around, to a great height. The seats were all of stone, and at regular intervals between them were flights of steps for going up and down. In the centre, below, was a large level space, called the arena. All around the arena, and under the seats, were immense galleries or passage ways among the arches, some of which were below the level of the ground. Some of these galleries were for the spectators to use in passing from one part of the building to another, and others were used for the dens and cages of the wild beasts that were kept there to fight in the arena, for the amusement of the people.