In either case the slashing can be given the advantage of the greatest dryness with safety if it is surrounded by a cleared fire line from which to work. Firing should be against the wind and if the wind changes suddenly the opposite edge should be back fired. Previous cutting of all dead trees and snags over 25 feet high is urgently recommended. The camp crew should be held in readiness, well provided with tools, as insurance against accidental escape.
Its probable restriction of insect breeding is a point of slash burning likely to receive much future study. It is well known that most forest-injuring insects prefer dying trees to vigorous ones; also that the existence of an abnormal amount of such material tends to abnormal breeding and consequent serious attack of vigorous timber when the dead material becomes too dry to be inviting. It is by no means impossible that the supposed immunity of Douglas fir from insect injury may be largely due to the almost universal destruction by fire of logging debris which would otherwise afford ideal breeding places.
FIRE LINES
The division of mature forest into compartments separated by fire lines is seldom practicable in this country. Nevertheless slashings, deadenings and similar fire traps can very often be profitably confined by the cleaning of strips which will not only stop or retard the progress of a moderate fire but also facilitate patrol, fire fighting or back firing. On favorable ground, where some choice is offered, much may be done by falling timber inward so as to leave few tops near the uncut timber and by the location of skidroads. So far as practicable fire lines should be on the tops of ridges, for, being slower to go downhill than up, fire is more easily discouraged just as it reaches a crest. Bottoms of gulches are next in strategic value, and midslopes least.
SAFEGUARDING EQUIPMENT
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.