"The wood and foliage of coniferous trees like spruce, fir, and pine are so full of turpentine and resin that they burn like tinder. The heat is almost beyond the power of words to express. The fire does not seem to burn in a steady manner, the flames just breathe upon an immense tree and it becomes a blackened skeleton which will burn for hours.
"The actual temperature in advance of the fire is so terrific that the woods begin to dry and to release inflammable vapors before the flames reach them, when they flash up and add their force to the fiery hurricane. It is almost unbelievable, too, the way a crown-fire will jump. Huge masses of burning gas will be hurled forth on the wind and ignite the trees two and three hundred yards distant. Fortunately, fires of this type are not common, most of the blazes one is likely to encounter being ground fires, which are principally harmful in that they destroy the forest floor."
"But I should have thought," said Wilbur, "that such fires could only get a strong hold in isolated parts where nobody lives."
"Not at all. Sometimes they begin quite close to the settlements, like the destructive fire at Hinckley, Minnesota, in 1894, which burned quietly for a week, and could have been put out by a couple of men without any trouble; but sometimes they start in the far recesses of the forest and reach their full fury very quickly. Of course, every fire, even the famous Peshtigo fire, started as a little bit of a blaze which either of you two boys could have put out."
"How big a fire was that, sir?" asked Fred.
"It covered an area of over two thousand square miles."
"Great Cæsar!" ejaculated Wilbur after a rapid calculation, "that would be a strip twenty miles wide and a hundred miles long."
The Chief Forester nodded.
"It wiped the town of Peshtigo entirely off the map," he said. "The people were hemmed in, ringed by fire on every side, and out of a population of two thousand, scarcely five hundred escaped. Flight was hopeless and rescue impossible."
"And could this have been stopped after it got a hold at all?" asked Wilbur seriously, realizing the gravity of the conditions that some day he might have to face. "Could not something have been done?"