10 BULLETIN 824, U. S. DEPARTMENT OF AGRICULTURE 
power the shaft is turned, and the two stones roll around, one after the 
other, on a heavy block of granite. These millstones, which are also 
of granite, are about 214 feet in diameter by 8 inches thick, and weigh 
several hundred pounds each. Flowers imported into this country 
are received in bales done up in burlap, containing on an average 
about 440 pounds neteach. The contents of the bales are emptied on 
the floor, and any large stones, which are sometimes added to give 
weight, removed. The flowers are then shoveled or dumped into the 
box which surrounds one of these stone chaser mills, where they are 
kept in the path of the revolving stones, which are mounted about 2 
feet apart, by meansofarevolvingarm. The flowers are scon reduced 
to a fine dustlike powder, which in some mills is periodically shoveled 
out and in others is removed from pockets in the sides of the inclosing 
box. The powder is so fine that it is carried up by the air currents 
roduced by the revolving stones, and settles into pockets provided 
or that purpose. The top, as well as the sides of the mill, is boxed in 
very tightly to keep the powderfrom flying everywhere. After grind- 
ing, the powder is put through a sieve or bolted, and the tailings re- 
ground. In some cases a sieve of only 40 meshes to the inch is used, 
whereas other firms employ 110-mesh bolting cloth. 
The steel disk mill, used by some firms in grinding insect flowers, 
consists of a series of perforated steel disks with lugs on the edge which 
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 disks. The disks 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 disks, 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 disk mill, 
or they may be run first through a cutter, which further breaks them 
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. 
