278 AMERICAN FORESTRY 



upon proper preventive measures in clearing lands they have succeeded in 

 preventing' serious dama<;e in most cases. 



More dillicult to handle have proved cases of malicious incendiarism. It 

 is a matter of experience that evil doers in North America can much more 

 easily escape the eye of the law than in European countries, simply because 

 of the greater area and more numerous hiding places, and the lynch-law sys- 

 tem as coniMionly practised can hardly improve the matter, as in such cases 

 an innocent party is taken and punished for the guilty even more frequently 

 than in the case of other crimes. Fortunately the number of malicious fires 

 in the United States has probably never been great. But besides these human 

 lire-setters, there is a natural one which assumes importance in the least ac- 

 cessible districts, namely, lightning. In the North American west fires are 

 started by lightning with uncommon frequency, and as many storms there 

 yield hardly any rain, the flames which follow it are not as a rule extinguished 

 as in the east. From his investigations in the San Francisco mountains of 

 Arizona, J. B. Leiberg, the most distinguished expert of the United States 

 Geological Survey, came to the conclusion that in this reservation by far the 

 greatest number (about sixty per cent) of all fires are caused by lightning. 



And this brings us to another principal factor which must be considered 

 responsible for the rise and spread of forest fires in North America the cli- 

 mate. It has long been known not only that the North American climate is 

 much drier than the European, but that in the west the drought is long-con- 

 tinuing, even to the point of complete rainlessness, while in the east, in spite 

 of the large annual rainfall, there are periods of drought of greater or less 

 length. What effects are produced by such a climate on the forest and its 

 intlammability can be readily understood. In Germany, double precautions 

 are taken in dry years, and in spite of this the fire damage increases in such 

 years; in North America, the highest possible degree of care is demanded 

 every year, and in dry years the greatest conceivable care is insufiicient to 

 prevent the spread of individual fires over immense areas. Such a year in the 

 east was 1908 with its gigantic conflagrations, in the west 1910; so that we 

 are not to presuppose for such years an unusual number of malicious or 

 negligent persons, for natural conditions are without doubt principally re- 

 sponsible in these special cases. The forest-floor of the western woods with 

 its dry pine-needles, twigs, moss, grass and general undergrowth and its 

 millions of dead trunks thrown down by storms forms in late summer and 

 autumn a tinder which can be set off by any small spark; but in the present 

 year, in which the summer drought set in in the middle northwest unusually 

 early and was extremely severe, it was still drier than usual, and fires had 

 passed human power to control before their existence was known. 



Since the woods of the west consist principally of conifers, whose large 

 content of rosin makes them much more inflammable than other trees, it is 

 to be jiresumed that the destruction was very complete. Certain species, how- 

 ever, more particularly the yellow pine, ofler a great resistance to forest fires, 

 and where tliey stand unmixed and without any great undergrowth they 

 friMjucntly escai)e being killed. For this reason even in the dryest parts of 

 the west, such as Utah, Nevada, Arizona and New Mexico, where there are 

 many pure stands of yellow pine, the destruction by fire is seldom so radical 

 as in the less dry areas of Idaho, Montana, Washington and Oregon, in which 

 the stands are usually mixed and in addition present a ground covering which 

 is very combustible after it has been exposed to the summer drought; besides, 

 the numerous standing dead trees, and areas of dead trees, which have been 

 killed off by insects or other conditions, are highly favorable to the spread of 

 fires in the forests of the northwest. 



