12 BULLETIN- 824, U. S. DEPARTMENT OF AGRICULTURE. 
revolve in a corrugated cylinder at a rate of from 3,000 to 3,500 revo- 
lutions per minute. The flower heads are fed into a hopper, either by 
hand or automatically through a chute, and are thrown with great 
force against the corrugations on the inside of the cylinder by the re- 
volving discs. The discs do not rub against each other or the cylin- 
der ; the flowers are simply cut to pieces by the force of their impact 
against the sharp corrugations. In a mill of this kind the cylinder 
opens into a large box or cloth bag of close weave. If a box is used, 
it must be provided with a number of cloth "chimneys, " which may 
be supported by a wooden framework. The idea of the cloth is to 
hold in the fine insect powder while allowing the air, which is fanned 
into a very strong current by the revolving discs, to filter through. 
When flowers imported from Japan are ground it is necessary first 
to run them through a disintegrator, which consists commonly of a 
mill built like an ordinary large, coarsely-grinding domestic coffee mill. 
Before being shipped from Japan, insect flowers are wrapped in rattan 
or similar material, and compressed into as small a bulk as possible in 
a press. Ordinarily four of these little bales, each of which weighs about 
100 pounds, are wrapped together in burlap with metal bands and 
wooden strips for shipment. The flowers are so compressed in these 
packages that the use of the disintegrator is necessary. From the 
disintegrator the flowers travel on a belt to a chute through which they 
fall to the floor below. An electromagnet is so arranged under the 
belt that particles of iron, like nails, which may be present in the bale, 
are removed as the flowers pass down the chute. On the floor below 
the flowers may be fed directly into the hopper of the disc mill, or they 
may be run first through a cutter, which further breaks them up and 
expedites the final pulverization. 
In either process the powder becomes quite warm in the grinding, 
thus losing part of its moisture, but not, apparently, any of its insecti- 
cidal constituents. This loss in moisture, together with a slight 
mechanical loss in the milling process, amounts to 6 or 7 per cent by 
weight of the flowers ground. 
In grinding insect flowers it is not customary to add any material 
to assist the pulverization. Xor, with the exception of large stones, 
which may have been added to the bale, and certain bits of iron which 
are taken out by an electromagnet, is anything removed from the 
flowers as they are received. Such foreign matter as stems, either 
adhering or loose, sand, and dirt is allowed to remain. 
In Japan the process of manufacture is as follows (292) : The 
flowers are dried in the shade for one day in the summer, after which 
some 8 pounds are placed in a stone mortar and powdered for about 10 
hours. This powder is then put through a sieve, and dried by steam 
heat at from 80° to 90° for 4 or 5 hours in a drying room. When well 
dried it is packed in tin containers. In the sieving process from 20 
