Modern Imp'ovemenif in Corn-MilUng Machinei'i/. 83 
The wheat thus imperfectly cleaned was " fed " into the 
ordinary millstone, which had in the better mills been improved 
from a very rough and primitive machine by the elaboration of 
every part of the apparatus into a very perfect machine, capable 
in every part of the most accurate adjustment, and lacking in no 
mechanical refinement. It is unnecessary to describe millstones, 
as they are, or were, familiar to every one. Suffice it to say 
that, up to about thirty-five or forty years ago, the object of the 
miller was to reduce the wheat at one grinding to flour and 
" offal," and he succeeded best who separated the two elements 
of the wheat — namely, the flour of the interior of the berry, 
and the rind or skin — most completely at one grinding. 
The " meal " produced by the grinding was then " dressed " — 
that is, divided by sifting — and ideally perfect work meant that 
the flour- should contain no particle of skin, and the offal or skin 
should have no particle of flour left upon it. In the language 
of the mill there must be clean flour and clean ofial. No ap- 
proach, however, to theoretical perfection was ever attained. 
The flours always contained specks of the skin broken up in the 
triturating process of millstone-grinding, and the brans or other 
descriptions of offal were never perfectly free from flour. It was 
always the aim of the miller to increase the quantity ground per 
j pair of stones per hour, limited by the greater necessity of 
[ making " good work " in the way of separation ; but in this object 
he was constantly thwarted by the impossibility of " cleaning 
the offal " properly, and by the production of too much heat, to 
the injury of the flour, by the additional friction. 
The introduction of" the exhaust " — i.e. the withdrawal of the 
heated air and moisture by a fan from the cases which enclosed 
j the millstones — and of the " blast and exhaust " — a combination of 
the " exhaust " by one fan, and the " blast " or forcing of air 
between the surfaces of the millstones by another fan — had for 
its chief object the increase of the working capacity of the mill- 
stone, by keeping down the temperature of the " meal." But 
whether ventilation was used or not, it was found that increase 
of the rate of grinding had for one result the production of an 
intermediate article, neither offal nor flour, composed chiefly of 
small particles of the hardest portion of the farinaceous part of 
the wheat-corn, either alone or attached to a minute particle 
of the skin. These particles, mixed with particles of the skin of 
the same size, were the product termed " middlings." 
" Middlings " were simply particles of the wheat imperfectly 
ground, and were reduced to flour by regrinding on a separate 
; pair of millstones. The resultant flour, if the middlings were 
I tolerably free from particles of bran, was found to be better than 
the flour of the original wheat-grinding, as was natural, because 
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