“Oh, it’s because—because I’m so glad we’re—we’re here—safe!” sobbed the girl.
“Oh!” exclaimed Tom, but there was a great deal of meaning in that one word. “Yes, I guess we’re all right,” he agreed.
He looked out of the cave. In front of it and on either side the fire was burning fiercely. Another few seconds and neither he nor Mary would have been able to get through that fierce, hot barrier. But the flames could not eat their way into the cavern.
Then, as he and the girl stood there, thankfulness in their hearts that they had thus come safely through two grave dangers, there suddenly sounded a deep, booming, vibrating sound that seemed to shake the earth about them.
“Dynamite!” cried Tom. “They’ve brought up explosives and are blowing up patches to stop the flames. A good idea!”
“No, that isn’t dynamite,” said Mary. “Don’t you know thunder when you hear it?”
“Thunder?” cried Tom Swift.
“Yes. It’s thundering! Don’t you remember, we saw signs of a storm coming up in the west just before the aeroplane went dead?”
“That’s right. If it is thunder——”
A booming crash interrupted him. There was no doubt of it, a heavy storm was pending.