The most fruitful source of fires is spark-emitting locomotives and logging engines. Much data has been collected showing that with oil at a reasonable price its use is economical from a labor-saving point of view as well as from that of safety. It reduces expense for watchmen, patrol, fuel cutting, firebox cleaning and firing. And since it is an absolute prevention, while all other measures merely seek to minimize the risk, it is probable that even where the cost of the oil more than balances these savings it will save in the long run by averting a costly fire. Where the use of oil cannot be considered, spark arresters are essential. The argument that they prevent draft is not worth attention. It is greatly exaggerated by engineers and firemen prejudiced against innovation or too inattentive to keep their fires up properly and consequently unnecessarily dependent on occasional forced draft. The slight disadvantage involved by the modern improved arrester is not to be compared with the importance of the safety acquired. In addition to spark arresters, which may fail or be out of order, logging engines using fuel other than oil should be provided with a constant tank or barrel supply of six to twelve barrels of water and 100 feet of hose with proper pumping attachment. With this a spark fire can be promptly soaked out beyond danger of invisible smouldering in rotten wood or duff. When conditions are dangerous, careful loggers send a man back to each donkey-setting between supper and bedtime to look for possible fires that were not seen when the crew left. Many keep a watchman on the rounds all night. Railroad rights of way can usually be kept cleaned and burned at a cost far less than that of otherwise frequent shutdowns of the entire camp to fight fire or rebuild bridges, to say nothing of loss of timber. PATROL The best way to prevent fire is to prevent it. Putting out fires already started is better than letting them burn, but as the real foundation of a protective system it is about like lowering a lifeboat after the ship has struck. Only by patrol can the incipient spark or camp fire be extinguished before it becomes a forest fire that has to be fought, taking hours or days instead of minutes. One patrolman can stop 100 incipient fires easier than 100 men can stop one big fire. Fires in the forest may never be wholly averted, but patrol will prevent them from becoming "forest fires."