He rushed off toward the river, and came back in a few minutes with a piece of clear ice, almost as large as his palm, and an inch or two thick. He slipped off his mittens, and began to rub it between his hands, so as to melt it down with the heat of his skin.
"See what it is? Burning-glass!" he exclaimed.
"But you can't make a burning-glass of ice!" said Maurice.
"Why not? Anyhow, I'm going to try."
But before he had worked the ice long, he had to stop, for his hands seemed freezing. While he beat and rubbed them, Maurice, incredulous but willing, took the lump of ice, and shaped it down while the heat lasted in his hands. He then passed it on to Macgregor, who in turn handed it to Fred again. He finally succeeded in melting and curving it roughly into the proper shape.
He tried it on the back of his hand. An irregular but small and intensely hot spot of light concentrated itself there.
"I do believe it will work!" Peter cried.
They hastily collected a handful of fine, dry hair moss from the fir branches, and peeled filmy shreds of birch bark. Fred brought the "glass" to bear on the little heap. His numbed hands trembled so that he could hardly hold it still. For some time there was no result. Then a thin thread of smoke began to arise. The boys held their breath. The hair moss suddenly sparkled and flamed. A shred of bark caught. Peter interposed a large roll. It flared up.
"Hurrah! We've got it!" cried Macgregor. "Fred, you've saved our lives, I do believe."
They piled on twigs, branches, and heavy lumps of wood, and soon had a brisk fire going. Better still, they were now assured of having always the means of making one—at least, whenever the sun shone.