_Specification of, and Observations on, the Construction and Use of the
best Horizontal Sugar-mill._
_Fig._ 1075. Front elevation of the entire mill. _Fig._ 1076. Horizontal
plan. _Fig._ 1077. End elevation. _Fig._ 1078. Diagram, showing the
dispositions of the feeding and delivering rollers, feeding board,
returner, and delivering board.
[Illustration: 1075 1076]
_Fig._ 1075. A, A, solid foundation of masonry; B, B, bed plate; C, C,
headstocks or standards; D, main shaft (seen only in _fig._ 1076.); E,
intermediate shaft; F, F, plummer-blocks of main shaft D, (seen only in
_fig._ 1076.); H, driving pinion on the fly-wheel shaft of engine; I,
first motion mortise wheel driven by the pinion; K, second motion
pinion, on the same shaft; L, second motion mortise-wheel, on the main
shaft; M, brays of wood, holding the plummer-blocks for shaft D; N,
wrought-iron straps connecting the brays to the standards C, C; O, O,
regulating screws for the brays; P, top roller and gudgeons; Q and R,
the lower or feeding and delivering rollers; S, clutch for the connexion
of the side of lower rollers Q and R, to the main shaft (seen only in
_fig._ 1076.); T, T, the drain gutters of the mill-bed (seen only in
_fig._ 1076.).
The same letters of reference are placed respectively on the same parts
of the mill in each of _figs._ 1075, 1076, and 1077.
[Illustration: 1077 1078]
The relative disposition of the rollers is shown in the diagram, _fig._
1078., in which A is the top roller; B, the feeding roller; C, the
delivering roller; D, the returner; E, the feed board; F, the delivering
board.
The rollers are made two inches and a quarter to two inches and a half
thick, and ribbed in the centre. The feeding and delivering rollers have
small flanges at their ends (as shown in _fig._ 1075.), between which
the top roller is placed; these flanges prevent the pressed canes or
begass from working into the mill-bed. The feeding and top rollers are
generally fluted, and sometimes diagonally, enabling them the better to
seize the canes from the feed-board. It is, however, on the whole,
considered better to flute the feeding roller only, leaving the top and
delivering rollers plane; when the top roller is fluted, it should be
very slightly, for, after the work of a few weeks, its surface becomes
sufficiently rough to bite the canes effectively. The practical
disadvantage of fluting the delivering rollers, is in the grooves
carrying round a portion of liquor, which is speedily absorbed by the
spongy begass, as well as in breaking the begass itself, and thus
causing great waste.
The feed board is now generally made of cast iron, and is placed at a
considerable inclination, to allow the canes to slip the more easily
down to the rollers. The returner is also of cast iron, serrated on the
edge, to admit the free flowing of the liquor to the mill-bed. The
concave returner, formerly used, was pierced with holes to drain off the
liquor, but it had the serious disadvantage of the holes choking up with
the splinters of the cane, and has therefore been discarded. The
delivering board is of cast iron, fitted close to the roller, to detach
any begass that may adhere to it, and otherwise mix with the liquor.
In Demerara, Surinam, Cayenne, and the alluvial district of Trinidad, it
is usual to attach to the mill a liquor-pump, with two barrels and three
adjustments of stroke. This is worked from the gudgeon of the top
roller. In action, the liquor from the gutter of the mill-bed runs into
the cistern of the pump, and is raised by the pump to the gutter which
leads to the clarifier or coppers. Such pumps have brass barrels and
copper discharging pipes, are worked with a very slow motion, and
require to be carefully adjusted to the quantity of liquor to be raised,
which, without such precaution, is either not drawn off sufficiently
quick, or is agitated with air in the barrels, and delivered to the
gutter in a state of fermentation.
In working this mill, the feeding roller is kept about half an inch
distant from the upper roller, but the delivering roller is placed so
close to it, as to allow the begass to pass through unbroken.
The practice with this mill is to cut the sugar canes into short lengths
of about three feet, and bring them to the mill tied up in small
bundles; there the feeder unties them, throws them on the feed board,
and spreads them so that they may cross each other as little as
possible. They are taken in by the feed rollers, which split and
slightly press them; the liquor flows down, and, the returner guiding
the canes between the top and delivering rollers, they receive the final
pressure, and are turned out on the mill-floor, while the liquor runs
back and falls into the mill-bed. The begass, then in the state of
_pith_, adhering to the skin of the cane, is tied up in bundles, and
after being exposed a short time to the sun, is finally stored in the
begass-house for fuel. By an important improvement in this stage of the
process, recently introduced, the begass is carried to the begass-house
by a carrier chain, worked by the engine.
The relative merits of horizontal and vertical sugar-mills on this
construction, may be thus stated:--The horizontal mill is cheaper in
construction, and is more easily fixed; the process of feeding is
performed at about one-half of the labour, and in a much superior
manner; the returner guides the canes to receive the last pressure more
perfectly; and the begass is not so much broken as in the vertical mill;
but left tolerably entire, so as to be tied, dried, and stored, with
less trouble and waste.
The vertical mill has a considerable advantage, in being more easily
washed; and it can be readily and cheaply mounted in wooden framing; but
the great labour of feeding the vertical mill, renders it nearly
inapplicable to any higher power than that of about ten horses. In
situations where the moving power is a windmill, or a cattle gin, the
vertical mill may be preferred.
The scale of produce of such mills varies according to the climate and
soil. In Demerara, a well constructed engine and mill will produce about
100 gallons of liquor per hour for each horse power.