4 BULLETIN 328, U. S. DEPARTMENT OF AGRICULTURE. 
checks in each experiment are comparable with the samples con- 
taining the different impurities. 
The wheat used in the experiment was thoroughly cleaned and 
scoured before making up the milling samples containing the various 
admixtures of rye, corn cockle, kinghead, and hairy vetch. This was 
done because the samples were neither cleaned nor scoured after the 
mixing, since it was desired that a definite known percentage of any 
added impurity should go to the rolls for milling into flour, bran, and 
shorts. 
Each sample milled consisted of 100 pounds, including the impurity 
(e. g., 99 pounds of wheat and 1 pound of corn-cockle seed; 98 pounds 
of wheat and 2 pounds of corn cockle seed, etc.). The samples were 
Fig. 1. — Grains of rye (A) and wheat (B); seeds of corn cockle ( C), hairy vetch (D), kinghead (JE), and 
wild vetch (F). On account of the shape, size, and specific gravity of these impurities they are not 
easily separated from wheat. (Natural size.) 
milled at the North Dakota Agricultural College in the experimental 
mill, which has a capacity of 50 barrels per day of 24 hours. 
To obtain results which would be comparable with average com- 
mercial conditions at country points, the methods of milling used in 
country mills were followed in general in the tests with the so-called 
inseparable impurities. The flour yields obtained compare very favor- 
ably with those secured by well-equipped country mills of 50 to 100 
barrels daily capacity, since it was possible in milling the samples to 
make five breaks and as many reductions as desired, up to seven or 
eight. 
In the tests covering the three years, the samples were milled as 
straight flours (that is, only one grade of flour was made from the 
