ee 
438 
horse power, 36 feet long, 18 broad, and 83 high; 
for one of six-horse power, 40 feet long, 20 broad, 
and 9 high; and for one of eight-horse power, 44 
feet long, 21 broad, and 9 high. A suitable drum 
for a machine of two-horse power is 23 feet long, 
and makes 180 revolutions per minute; for one 
of four-horse power, is 3 feet long, and makes 
300 revolutions per minute; for one of six-horse 
power is 34 feet long, and makes 320 revolutions 
per minute; and for one of eight-horse power, is 
4 feet long, and makes 340 revolutions per mi- 
nute. Suitable feeding-rollers for a machine of 
two-horse power are 2 feet 7 inches long, and 
make one revolution for every 43 or 6} revolu- 
tions of the drum; for one of four-horse power 
are 3 feet 1 inch long, and make one revolution 
for every 4} or 6 revolutions of the drum; for 
one of six-horse power are 3 feet 7 inches long, 
and make one revolution for every 4 or 52 revo- 
lutions of the drum; and for one of eight-horse 
power are 4 feet 1 inch long, and make one 
revolution for every 3? or 54 revolutions of the 
drum; and all, for whatever amount of horse 
power, have the same diameter. The form of 
the apron, the position of the rakes, the diameter 
of the fans, and the form of the screen are the 
same for all powers; but the diameter of the 
rakes is variable; and the breadth of the fans 
for a two-horse power is 15 inches, for a four- 
horse power 18 inches, for a six-horse power 21 
inches, and for an eight-horse power 24 inches. 
The drum of some thrashing-machines is armed 
with beaters, and that of others with scutchers. 
This diversity occurred even in the original ma- 
chines of Meikle’s patent; and it has been con- 
siderably modified and extended in subsequent 
inventions. The beater stands out rectangularly, 
and strikes with a flat edge; and the scutcher 
stands out at an acute angle, and strikes with a 
somewhat sharp edge; and, in improved machines 
_ by different inventors and millwrights, the latter 
has a considerable diversity of both inclination 
and form. The action of a beater may be under- 
stood by supposing a handful of corn to be held 
in the hand, and to have its ears struck with the 
flat sides of a thin strip of wood; and the action 
of a scutcher, by supposing a sharp blow to be 
given, not on the ears, but in the direction of 
| them, and not with the flat sides of the strip of 
wood, but with its thin edge. Beaters appear to 
do always best, as to at once the quantity, the 
quality, and the cost of the work, in cases of 
heavy corn, loose in the husk, wheat, pease, and 
beans; and scutchers are cheaper, and sometimes 
more efficient, in all or most cases of barley and 
oats. But, to adopt the opinion and the words 
of Mr. Ransome, “although the operation of 
scutching may be performed at less expense of 
power, if partially executed, and that a greater 
quantity of straw may pass the machine, and 
consequently more corn may be obtained in a 
given time, yet, unless the scutchers are placed 
very near the concave, the work will be imper- 
THRASHING MACHINES. 
fectly performed, and much of the corn will re- 
main in the straw, and escape. But, if placed so 
near aS is requisite for clean thrashing, the lia- 
bility to break off the ears will be increased, which 
will involve the need of rethrashing; and the 
friction, from the narrowness of the interval, will 
then require, to the full, as great power as the 
beaters.” An improved system of beaters was in- 
troduced to notice, in 1839, by Mr. Ritchie of 
Banff; and consists in the use of eight half beat- 
ers instead of four entire ones,—four of the halves 
being placed intermediately to the other four,— 
each having but half the resistive power of an 
entire one,—and all so operating as to equalize the 
ageregate resistance by means of the increased 
frequency and double distribution of the strokes. 
The shaker of most thrashing machines con- 
sists simply of revolving rakes, and, in very many 
instances, is so constructed as both to involve 
very considerable waste of moving power, and to 
allow a considerable portion of the grain to be 
carried away.—A new mode of shaking, invented 
in 1839 by Mr. Docker of Finden in Banffshire, 
comprises a peculiar arrangement of two series 
of light batons of wood by means of cranks, to 
which each series are separately attached, the 
batons 1, 3, 5, &c. forming the one series, and 
the batons 2, 4, 6, &c. forming the other; and 
their motion is saltatory and alternately pro- 
gressive, and causes the straw to pass both verti- 
cally and horizontally forward.—Another shaker, 
invented in the same year by Mr. Ritchie, is the 
same in principle as Mr. Docker’s, but differs 
slightly in the method of producing the motion 
of the batons—A shaker, invented in 1840, by 
Mr. Archibald Ainslie of Peaston, is simply a 
large skeleton cylinder, framed of wood covered 
in the interior with trellis-work, but entirely 
open at both ends. It lies at an angle of about 
13°, and rests upon four plain square-edged pul- 
leys; and the driving of two of the latter by the 
machine, gives motion by contact to the cylinder. 
—A small shaker of the common rake-form is usu- 
ally placed between the drum and the cylinder, 
by which the straw is delivered into the latter ; 
and when a portion of straw has entered the 
cylinder, it is carried round till it reach the apex, 
when it falls to the lower side at a point some- 
what in advance of that at which it first began 
to ascend. When the portion of straw has again 
reached the apex, a second fall occurs to a point 
still more in advance, and so on until discharged 
at the lower end. A succession of such parcels 
of straw are, of course, in constant progress 
through the cylinder, rising and falling from five 
to seven times in their _passage-——An improve- 
ment of a very simple and obvious kind, intro-. 
duced in 1840 by Mr. Shennan of Lairdlaugh. in 
Dumfries-shire, consists in the application of a 
screen in the place of the second shaker commonly 
employed. The screen lies at an angle of about 
20°, jointed at the upper end to the mill-frame, 
and is kept in rapid vibration by a short crank 
