_Causes of Forest Fires on the National Forests._ Forest fires on the National Forests originate in many different ways. In 1917, lightning caused 27 per cent.; unknown agencies, 17 per cent.; campers, 17 per cent.; incendiaries, 12 per cent.; railroads, 13 per cent.; brush burning, 7 per cent.; saw mills, 3 per cent., and all other causes, 4 per cent. Thus it will be seen that a very large percentage, at least 60 per cent., of the fires are attributable to human agencies and are therefore preventable. At least 27 per cent, of the fires, those attributed to lightning, are not preventable, and the only way to combat those is for the Forest officer to get to them as soon as possible after they get started. The preventable fires, however, may be arrested at their source, that is, by popular education dealing with the use of fire in the woods these causes can be greatly reduced and, in time, no doubt, eliminated. Therefore, the fire protection problem immediately resolves itself into two almost distinct phases of action--fire prevention and fire control. [Illustration: Figure 34. A forest fire lookout station at the summit of Mt. Eddy. Mt. Shasta in the background, California] Just how these various agencies start fires may be of interest. Railroads cause fires by their locomotives sending out sparks through the smokestack or dropping hot ashes along the right-of-way. These sparks alight in inflammable material, such as dry grass and leaves, and start a fire. Lightning sets fire to trees, especially dead and dry ones. In the California mountains, lightning storms without rain are frequent and these do great damage. The author has seen as many as nine forest fires started by a single lightning storm inside of half an hour. Incendiary fires are set by people with varying intent. How many are set with malicious intent, just to see the forests burn, is not known, but many fires are started by people setting fires to drive game, to improve the pasture, to make traveling through the woods easier, or for other reasons. Brush burning includes those fires which start from settlers clearing land and burning the brush and thickets. Campers cause a large percentage of the fires by leaving their camp fires burning. Instead of extinguishing them before they leave camp, careless people let them burn; a wind blows a few sparks into some dry leaves or grass nearby, and the fire is started. Many forest fires also start around logging camps by sparks escaping from logging engines, or by setting fire to the slash that is left after logging and allowing these fires to get beyond control.