Up from the edge of the brook they ran and into the cool, dark and friendly shelter of the cave. They reached it only just in time, for they were no sooner inside than a shower of sparks and burning brands, falling into some dry sticks, leaves and grass near the mouth of the cavern, sent a sheet of flame directly across it. “Now let the fire burn itself out—and it won’t take long at this rate!” cried Tom, as he and Mary stood in comparative safety, free from the menace of fire and out of that blinding, choking smoke. Then, to Tom’s surprise, Mary burst out crying. CHAPTER XIV A QUEER ATTACK THE young inventor, not much accustomed to tears, thought at first that Mary had been hurt in some way, perhaps burned by a flying brand. “What is it? Tell me,” he urged, taking her in his arms as they stood in the cool darkness and safety of the cave. “I’m—I’m all right!” gasped Mary, looking up at him as well as she could in the gloom. “All right? Then, why are you crying?” “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. “The rain will put out the forest fire,” concluded Tom. “Then we can get out of here and back home.” “Home seems a long way off,” sighed Mary. “We can make it pretty quickly by going down the brook,” suggested Tom. “The brook always rises a short time after even a little rain, for all the water in this section drains into it. I know where there’s a boat hidden in the bushes not far from here, and we can paddle down in that.” “It sounds enticing,” returned Mary. “Oh, I look a fright, don’t I?” she asked, with a nervous giggle. Having been in the cave a little while, their eyes were more accustomed to the gloom and they could see better. “You do not!” emphatically cried Tom, which, of course, was the right answer.