_Causes of fire._ Forest fires are due to all sorts of causes, accidental and intentional. Dropped matches, smouldering tobacco, neglected camp fires and brush fires, locomotive sparks, may all be accidental causes that under favorable conditions entail tremendous loss. There is good reason to believe that many forest fires are set intentionally. The fact that grass and berry bushes will soon spring up after a fire, leads sheep men, cattle and pig owners, and berry pickers to set fires. Vast areas are annually burned over in the United States for these reasons. Most fires run only along the surface of the ground, doing little harm to the big timber, and if left alone will even go out of themselves; but if the duff is dry, the fire may smoulder in it a long time, ready to break out into flame when it reaches good fuel or when it is fanned by the wind, Fig. 105. Even these ground fires do incalculable damage to seeds and seedlings, and the safest plan is to put out every fire no matter how small. [Illustration: Fig. 106. Burned Forest of Engelmann Spruce. Foreground, Lodgepole Pine Coming in. _U. S. Forest Service._] Altho it is true that the loss of a forest is not irremediable because vegetation usually begins again at once, Fig. 106, yet the actual damage is almost incalculable. The tract may lie year after year, covered with only worthless weeds and bushes, and if hilly, the region at once begins to be eroded by the rains. After the fire, may come high winds that blow down the trunks of the trees, preparing material for another fire, Fig. 107. [Illustration: Fig. 107. Effect of Fire and Wind. Colorado. _U. S. Forest Service._] The statistics of the actual annual money loss of the timber burned in the United States are not gathered. In 1880 Professor Sargent collected much information, and in the census of that year (10th Census, Vol. IX) reported 10,000,000 acres burned that year at a value of $25,000,000. In 1891, the Division of Forestry collected authentic records of 12,000,000 acres burned over in a single year, at an estimated value of $50,000,000. In the Adironacks in the spring of 1903, an unprecedentedly dry season, fire after fire caused a direct loss of about $3,500,000. In 1902, a fire on the dividing line between Washington and Oregon destroyed property amounting to $12,000,000. Within comparatively recent years, the Pacific Coast states have lost over $100,000,000 worth of timber by fire alone. During September, 1908, forest fires raged in Minnesota, Michigan, Wisconsin, Maine, New York and Pennsylvania. The estimates of loss for northern Michigan alone amounted to $40,000,000. For two weeks the loss was set at $1,000,000 a day. The two towns of Hibbing and Chisholm were practically wiped out of existence, and 296 lives were lost. Certain forest fires have been so gigantic and terrible as to become historic.