"Now I'll tell you how it was," went on the janitor.
"Yes, do," urged Mr. Tetlow. "We don't want it to happen again."
By this time the excitement had quieted down. There was no more smoke, and there was no smell of fire.
"I had started up the new heating boiler to try it," explained the janitor. "We didn't exactly need steam on to-day, though it is a bit cold, and it looks like snow. But I thought I'd try the new steam plant, so I built a fire in the boiler.
"I left it going and went off to do some work in another part of the school, and I guess I forgot about the steam. Anyhow, all at once I heard the roar and the rumble, and I felt the building shake. I knew right away what had happened, and I ran down cellar. I didn't even stop to explain to anyone."
"Well, what did happen?" asked the principal.
"Why, the safety valve got stuck, and when the pressure got too heavy it wouldn't let the steam escape. So the pipes, all through the school, were filled and the pressure was so strong that they commenced to shake and tremble. That made the building vibrate, and the boiler began to rumble and roar, too.
"I was afraid it might blow up, so down I rushed and opened the safety valve that was stuck shut. That let out the steam, and the pressure in the pipes went down. And that's all."
"It was enough," said Miss Williams. "So that white cloud was steam, and not smoke from a fire?"
"Yes, ma'am," answered the janitor, "it was only steam."