DUST EXPLOSIONS IN GRAIN SEPARATORS. 15 
1. Prevalence and distribution of static electricity in and about 
the separator. 
2. Inflammability of smut dust. 
3. Effect of introducing foreign material, accidentally or mali- 
ciously, into the separator. 
MEASUREMENT OF DISCHARGES OF STATIC ELECTRICITY. 
Both steel and wooden separators were tested while threshing both 
smutty and smut-free wheat and also oats. The common plan of pro- 
cedure was to establish a good reliable “ ground” by driving an iron 
rod deep into the earth, pouring water around it, and connecting 
one lead from a galvanometer to this rod. The other lead from the 
galvanometer was loose and was touched in turn to cylinder shaft, 
frame, blower, and all moving parts. 
On all machines tested strong discharges were obtained from 
almost every part of the machine to the ground, but in many cases 
the strongest appeared to be from the front wheels to the ground. 
Strong discharges were also obtained between the cylinder shaft and 
concaves, and slight ones between a moving and a stationary metallic 
part, and between any two moving parts. The galvanometer used 
in the tests was the ordinary two-coil instrument showing deflection 
and direction but not magnitude of the current. 
FIELD EXPERIMENTS. 
At the close of the threshing season three day tests were run on 
a donated separator in the field in northern Idaho, under as nearly 
actual threshing conditions as could be secured at that time. As it 
was impossible to obtain unthreshed smutty wheat, it was necessary 
to make use of straw mixed with loose smut secured from a local mill. 
At the time of the tests the temperature was at least 50 degrees below 
that prevailing during the threshing season, and the weather was 
unusually damp. Because of the conditions existing, the results of 
these tests can not be considered conclusive, but they tend to confirm 
the deductions made from the investigations in the field during the 
threshing season. 
STATIC ELECTRICITY AND ELECTRIFICATION OF SMUT DUST. 
The experimental work carried on during the investigations proved 
conclusively that, under favorable atmospheric conditions, static 
electricity is present on all types of machines. In the Pacific North- 
west humidity conditions during the entire threshing season are 
favorable for the production of static electricity. The air as a rule 
is very hot and dry, with the humidity on certain days as low as 7 
per cent, the average being about 17 per cent for the middle of 
the day. 
