14 
BULLETIN 927, U. S. DEPARTMENT OF AGRICULTURE. 
so slight that the extra handling would be unprofitable. However, 
such treatment seems to be necessary in order to make the subsequent 
drying by the rotary drier successful. If the seed contains more than 
52 to 55 per cent of moisture, it has a tendency to pack and stick to 
the walls of the drier instead of drying and discharging freely. In 
the experiments conducted none of the expeller or centrifuged seed 
packed in the drier, but in every case the untreated seed did pack. 
An experimental direct-heat drier (fig. 8) was installed for the 
work, the heat being supplied by gas. The seed-drying chamber of 
this machine wos 5 feet long by 1 foot in diameter and rotated at 
Fig. 8. — An experimental direct-heat drier. 
the rate of 16 revolutions per minute. About six or seven minutes 
were required for the seed to pass through the machine. Inasmuch 
as this period was too short for complete drying, several passages 
through the drier were necessary. Trials on a semicommercial scale 
demonstrated that such a machine is readily adapted to the drying 
of such material as washed tomato seed, since it is easily controlled, is 
continuous in operation, and carries a minimum labor charge because 
it requires but little attention. 
In order to produce seed of proper dryness it was necessary to 
pass it through the machine three times. The moisture content, 
which at the beginning was 5-2.4 per cent, at the end of each passage 
