Part 28 (1/2)

AGRICULTURAL MACHINES

THE THREshi+NG-MACHINE

Bread would not be so cheap as it is were the flail still the only rain from the straw What the cream separator has done for the dairy industry (p 384), the threshi+ng-ht therefore to be spared for this useful invention

[Illustration: FIG 226--Section of a threshi+ng226 a very coiven After the bands of the sheaves have been cut, the latter are fed into the -box on the top of the h velocity, and is fitted with fluted beaters which act against a steel concave, or breastwork, B, the grain being threshed out of the straw in passing between the two The breastwork is provided with open wires, through which s (short straws), and chaff passes on to a sloping board The straw is flung forward on to the shakers C, which gradually rain, etc, that has escaped the druh the shakers on to D, and works backwards to the _caving riddles_, orfan, N, sends air along the channel X upwards through these riddles, blowing the short straay to the left The grain, husks, and dust fall through E on to G, over the end of which they fall on to the _chaff riddle_, H A second colurain, seeds, dust, etc, fall on to I, J, and K in turn, and are shaken until only the grain re L to the elevator bottorain, carries it aloft, and shoots it into hopper P It then goes through the shakers Q, R, is dusted by the _back end blower_, S, and slides down T into the open end of the rotary screen-drurain travels gradually along it The first half of the screen has wires set closely together All the sh this, called ”thirds,” passes into a hopper, and is collected in a sack attached to the hopper h the second half of the drum, more widely spaced, into their sack; and the ”firsts” fall out of the end and through a third spout

MOWING-MACHINES

[Illustration: FIG 227]

The ordinary _lawn--ed knives, the edges of which pass very close to a sharp plate projecting fro the plate, giving a shearing cut to any grass that es The action is that of a pair of scissors (Fig 227), one blade representing the fixed, the other theknife If you place a cylinder of wood in the scissors it will be driven forward by the closing of the blades, and behappens with grass, which is so soft that it is cut right through

HAY-CUTTER

The _hay-cutter_ is another adaptation of the same principle A cutter-bar is pulled rapidly backwards and forwards in a fraround by a crank driven by the wheels through gearing To the front edge of the bar are attached by one side a nuular knives The fra forward horizontally Through slots in these the cutter-bar works, and its knives give a drawing cut to grass caught between them and the sides of the spikes

SOME NATURAL PHENOMENA

WHY SUN-HEAT VARIES IN INTENSITY

The reater will be the nus

228, 229, where A B is an equal distance in both cases The nearer the sun is to the horizon, the more obliquely do its rays strike the earth

Hence , and the tropics, where the sun stands overhead, are hotter than the temperate zones, where, even in summer at midday, the rays fall more or less on the slant

[Illustration: FIG 228]

[Illustration: FIG 229]