Modern Tmp'ovements in Coi'n-MiUing Machinery. 89 
ceous matter united with bran are commingled with the purer 
" semolina," and if all were ground together the impurity caused 
by the presence of bran would still enter the flour. It is there- 
fore necessaiy, still by air currents, to separate this branny 
" semolina " from the pure " semolina," and by breaking down 
the former separately to detach the bran from the pure flour- 
bearing cells. These latter may then be dealt with in the same 
way as the pure " semolina." 
There is also the germ of the wheat to be excluded from the 
flour. This is, from the miller's point of view, yellow, moist, 
oily matter, to be rigidly separated from the flour. It is sought 
to detach the germs in breaking down the wheat as far as 
possible unbroken, and then by sifting and the use of wind 
currents to concentrate them in one or more divisions of the 
"semolina"; these are passed through rollers with smooth sur- 
faces, by which the germ is flattened into flakes, while the 
" semolina " is reduced to powder, and the germ is then easily 
separated by sifting. These are but examples of the difficulties 
met with. The final product obtained is in the shape of flours 
of various grades of purity, according to the material and place 
in the process from which they come, and the offals. 
The principles on which the old and new systems of milling 
are based having been thus sketched, it is proposed to describe 
somewhat generally the modern mill and the machinery to be 
found in it. Among other changes that have occurred, perhaps 
one of the most marked is in the size of mills. Under the old 
system it was quite possible that a mill of very small capacity 
could be as efficient in proportion to its size as the larger mills. 
The larger mills contained only a repetition of the apparatus to 
be found in the smaller mills. But in " gradual-i'eduction " 
mills the work branches off" into so many divisions and sub- 
divisions of the products, that a lai-ge number of machines has 
to be provided each for a distinct employment, and for the full 
employment of each machine a certain minimum quantity of 
material is required. In large mills the provision both of 
material and feed is easy ; but in small mills both the room 
is lacking for the machinery, and the quantity of material to be 
manufactured would not provide sufficient work for the sub- 
ordinate machines even if they were present. It may perhaps 
be laid down that approximately 50 bushels per hour is the least 
quantity that can be dealt with propei'ly when working con- 
tinuously in a thoroughly well equipped mill ; while, in the mill- 
stone process, mills grinding as little as 6 or 8 bushels per hour 
did good work. The largest of the gigantic American mills is 
designed for grinding about 1,300 bushels per hour; but very 
few separate mill plants in this country exceed a capacity of 200 
