1654 AGRICULTURAT, MACHINERY AND IMPLEMENTS 



Department of Agriculture during the sinnnier of 1914 (i). The hypothesis 

 of spontaneous combustion of snmt-dust which was current at this time, 

 lacks confirmation. It was abandoned in favour of the theory of static 

 electricity. As at this date it was already suspected that the dust produced 

 during threshing had been the cause of accidents, the Department of Agri- 

 culture towards the end of the 1914 season procured samples of smut- 

 dust from threshing machines. This material proved to be extremely im- 

 flammable; it was necessary therefore to direct the investigation in this 



direction in order to solve the problem. 



This important question was examined b}- a number of experts from 

 the " Bureau of Chemistr}^ ", and from the " Office of Public Roads and 

 Rural Engineering ". In about 150 cases the investigators were on the 

 scene at the time of the explosion or very soon after. In some cases the 

 explosion was so sudden that the workmen could give ver}- little in- 

 formation. 



The accidents occuired most frequently from the end of July to the 

 end of August ; from 6 to 10 explosions each daj^ were recorded during this 

 period (2). From observations made in 128 different cases, the most critical 

 time of the day is from 2 to 7 p. m. In 81 per cent of the cases the fires were 

 put down to dust explosions ; in the other cases the flame produced was 

 small. Particular care was directed to the point of origin of the explosion 

 or fire : in 82 out of 108 cases observed (76 per cent), it was behind the 

 cylinder, or very close to it. 



Two hypotheses have been put forward to explain the fires : (i) incen- 

 diarism ; (2) natural causes. 



The first hypothesis has been discarded. There only remains the 

 second explanation and in 75 per cent of the cases the accident was 

 attributed to static electricity and to explosions of dust from smutty 

 wheat. 



The threshing machines were of many different kinds : the power used 

 does not seem to have any influence. In fact as manj^ explosions occurred 

 in machines driven by petrol motors as in those driven by steam. Out of 

 113 machines examined ; 18 had petrol motors, 93 were driven by steam 

 engines, I by an electric motor and i by horse power. Although the steam- 

 driven machines were in a great majority, they were not subject to more 

 frequent accidents, contrary to general opinion. 



The speed of the machine, although sometimes excessive, does not 

 seem to have any connection with the origin of the fire. 



Out of 112 explosions; almost all of which occurred during threshing, 

 the wheat contained from I to 35 % of smut. 15 % of the explosion.e occurred 

 with dirty wheat. Only 3 explosions occurred with perfectl.y clean heads. 



The question of hot axle boxes as a cause of fire was examined with 

 negative results. 



(i) See R. 1915, No. 536. 



(2) It was practically the same as in 191 4. 



