106 Modern Improvements in Corn-Milling Machinery. 
to be ground, and fitted with a roller or other feeding device by 
which the material is to be delivered to the meeting point of 
the rollers in a thin, regular, continuous stream, quite equal in 
volume at all points of the length of the rollers. Tlie feed 
must also be capable of adjustment to the greatest nicety, and 
is to be arranged so that the stoppage of the rollers or their 
being thrown apart instantly stops the delivery of the feed. 
There are devices innumerable for these and other subsidiary 
points about the roller-mill. To the lower side of the rollers 
are applied scrapers, for the purpose of removing any of the 
ground material which may stick to the rollers. Very fre- 
quently two pairs of rollers are arranged in one frame, all the 
rollers being parallel and in the same plane. A duplication of 
all the arrangements is then necessary. The material which 
has passed between the rollers is collected in a hopper below 
them, connected with a pipe which directs the stuff to any 
desired point. There is a very common arrangement by which 
three rollers are made to do duty as two pairs, the rollers stand- 
ing one above the other, the middle roller being common to 
each pair. All roller-mills are cased in so as to prevent the 
escape of dust, and, as the rollers become warm by friction in 
working, it is usual to draw away the warm air from the case by 
the application of an exhaust-fan. 
The motion is always conveyed to roller-mills by belts; 
sometimes each roller is driven by a separate belt ; in other 
examples each one of a pair is so driven, the other roller being 
driven off the spindle of the first by cog-wheels. But either in 
one way or the other each roller is separately driven. And it 
is necessary to do so, because there is always a difference in the 
speed of the two rollers of a pair, the difference being varied. 
The proportions of the speed are some such as 4 to 5, or 3 to 4, 
or 2 to 3, or 2, 3, 4, or 5 to 1. The mode of action is in fact 
that the goods are held and passed on by the slow roller, while 
the swifter movement of the fast roller in the case of the grooved 
rollers cuts the stuff up, and in the case of smooth rollers drags 
apart and disintegrates the particles to be reduced by a tearing 
action projDortionate in violence to the difference of the speed of 
the rollers and the amount of pressure applied. If a pair of 
smooth rollers be run at equal speeds, their action is simply to 
squeeze the particles that pass between them and flatten them 
so that they emerge in the form of small cakes or flakes, while 
those which are reduced by rollers driven at a differential speed 
come from them in a powdery condition fit for sifting. 
The ado])tion of the roller-mill has also demanded a modifi- 
cation of the dressing-machine or silk reel. For, especially with 
soft wlieats, there was discovered a tendency in the particles of 
