But there comes an evening when nobody thinks of going to bed. All day the smoke has become denser and denser, until it is no longer a haze, but a thick yellowish mass of vapor, carrying large particles of sooty cinders, filling one's eyes and nostrils with biting dust, making breathing oppressive. There is no escape from it. Closing windows and doors does not bar it out of the houses; it seems as if it could penetrate solid walls. Everything it touches feels rough, as if covered with fine ashes. The heat is horrible altho no ray of sunshine penetrates the heavy pall of smoke. In the distance a rumbling, rushing sound is heard. It is the fire roaring in the tree tops on the hill sides, several miles from town. This is no longer a number of small fires, slowly smouldering away to eat up a fallen log; nor little dancing flames running along the dry litter on the ground, trying to creep up the bark of a tree, where the lichens are thick and dry, but presently falling back exhausted. The wind has risen, fanning the flames on all sides, till they leap higher and higher, reaching the lower branches of the standing timber, enveloping the mighty boles of cork pine in a sheet of flame, seizing the tall poles of young trees and converting them into blazing beacons that herald the approach of destruction. Fiercer and fiercer blows the wind, generated by the fire itself as it sends currents of heated air rushing upward into infinity. Louder and louder the cracking of the branches as the flames seize one after the other, leaping from crown to crown, rising high above the tree tops in whirling wreaths of fire, and belching forth clouds of smoke hundreds of feet still higher. As the heated air rises more and more, rushing along with a sound like that of a thousand foaming mountain torrents, burning brands are carried along, whirling on across the firmament like evil spirits of destruction, bearing the fire miles away from its origin, then falling among the dry brush heaps of windfall or slashing, and starting another fire to burn as fiercely as the first. * * * There is something horrible in the slow, steady approach of a top fire. It comes on with the pitiless determination of unavoidable destiny, not faster than a man can walk. But there is no stopping it. You cannot fight a fire that seizes tree top after tree top, far above your reach, and showers down upon the pigmy mortals that attempt to oppose it an avalanch of burning branches, driving them away to escape the torture and death that threatens them. (Bruncken, _American Forests and Forestry_, 106-109.) [Illustration: Fig. 108. Fighting Forest Fire. _U. S. Forest Service._]