500 



ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



in timber amounted to 27,040,000 board feet, valued at $37,376. The 

 total cost of lii,diting the fires upon national forests and fires which 

 threatened national forest land was $'202,04G,3G. This does not in- 

 clude time spent by regular forest officers. 



The timbered area burned over per 1,000 acres was 1.78 acres in 

 1911, as against 1.86 in 1900, and 19.90 acres in the disastrous 1910 

 fire season. 



The number of fires during the season of 1911 and their causes 

 are set forth in the following table : 



Number of fires: 



Class A (no damage) 



Class B (under 5 acres burned) 

 Class O (5 acres or over) 



Total number of fires 



Causes of fires: 



Lightning 



Campers 



Eailroad locomotives 



Incendiary 



Brush burning 



Sawmills and donkey engines- 

 Unknown 



Miscellaneous 



Total , 



Number. 



1,571 



583 



1,215 



3,369 



948 

 574 

 442 

 225 

 199 

 33 

 743 

 205 



3,369 



Per cent. 



46.63 

 17.31 

 36.06 



100.00 



28.14 



17.04 



13.12 



6.68 



5.90 



.99 



22.05 



6.(» 



100.00 



A special study of lightning in relation to forest fires was completed 

 and published. This summarized 76,301 cases of trees struck by light- 

 ning on the national forests, together with manv thousands of cases in 

 the Eastern States. Lightning will always remain an unpreventable 

 cause of forest fires, and must therefore always be considered in the 

 protective scheme on the national forests. The records for the years 

 1907 to 1911, inclusive, show that 17.5 per cent of all forest fires on 

 national forests were caused by lightning. 



The table shows that 6.08 per cent of the fires were incendiary. 

 This is a slight increase over the number for the previous year. The 

 means for determining whether a fire is incendiary are better than 

 formerly, and some fires were doubtless classed as incendiary in 1911 

 that would have been counted of unknown cause in 1910. 



There are various ways of determining whether a fire is incendiary. 

 Usually a number of fires are started at the same time in one locality. 

 If there is no electric storm or other reason for such a series of fires, 

 the assumption is safe that it is due to incendiarism. In a number 

 of instances the observer at the lookout station has seen such a series 

 starting along a road or trail at just about the time interval required 

 to walk between the points. In several instancies tracks between the 

 starting points of a series of fires have indicated an incendiary origin. 

 Once a half-burned candle under a stump at the point where a fire 

 started showed the cause. In another case an ingenious contrivance 

 with a burning glass, a veritable infernal machine, w^as found. It is 

 very difficult to catch the incendiary in the act on account of the small 

 force at the disposal of the service. Several men have, however, been 

 apprehended and their cases are now before the courts. 



