6 



BULLETIN 379, U. S. DEPARTMENT OF AGRICULTTJRE. 



Early results prior to the opening of the threshing season indicated 

 that opinion as to the cause of explosions and fires of this nature was 

 divided between natural causes and incendiarism. The principal 

 reason advanced for this latter conclusion was that prior to the 1914 

 season explosions were not very frequent. This led to the conclusion 

 that means were being taken maliciously to destroy the separators by 

 introducing matches and explosives into the grain bundles. 



The following summary indicates the local opinion advanced as to 

 the causes of 121 explosions personally investigated during the 1915 

 season : 



Matches, incendiary, and acci- 

 dental 60 



Not given, and indefinite 14 



Foreign material, sparks from 



same 14 



Smut explosion 14 



Static electricity 10 



Powder or explosives - 4 



Engine sparks 2 



Bent spikes 1 



Hot boxes 1 



Crowding machine 1 



121 



Per 

 cent. 



Believed to be incendiary 49 



Foreign material 11 



Smut explosion 11 



Static electricity 8. 2 



Not given 11 



In connection with obtaining the opinions of the local thresher men 

 and the grain owners, a special effort also was made to secure any 

 evidence sustaining the conclusions advanced. In the great majority 

 of cases there was no definite reason for supporting the conclusion 

 which was based frequently on current rumors. In some cases, how- 

 ever, matches were found in the grain pan, but it was impossible to 

 determine whether they had fallen into the machines accidentally 

 or had been introduced intentionally. 



RESULTS OF FIELD INVESTIGATION. 



SUMMARY OF INVESTIGATORS' OPINIONS. 



In each explosion and fire the investigator summarized the evi- 

 dence obtainable, and after careful consideration of all information 

 available assigned the cause most probable in his opinion. The 

 following summary shows the conclusions reached in 94 special cases 

 investigated : 



Static electricity 1 45 Incendiary- 

 Smut explosion 25 Beater striking 



Friction sparks 10 No clue- 

 Matches 5 



Doubtful' 5 



Teeth striking - 1 



About 75 per cent of the occurrences were assigned to the presence 

 of static electricity and to smut explosions. The percentage assigned 



conveyor. 



1 

 1 



1 



94 



