The Evolution of Agricultural Implements. 239 
hoof and floor was obtained by allowing the beaters to force 
the grain against the ribs of a sparred concave placed below the 
drum and held in place by weighted levers. The corn was fed 
into the machine by means of fluted rollers, and while most 
of the threshed ears fell through the concave, such as passed 
away with the straw were separated from it by the action of 
a jogging screen, which received the latter on its exit from the 
drum. 
Two fans were used in Meikle’s machine, the first for 
separating the chaff, after which operation the partially cleaned 
grain was elevated into a scourer or hummel ler, whence it was 
discharged on to the screens of the second fan, thus completing 
the dressing. This “ double-blast ” system of cleaning was 
patented by Meikle and Machell in 1768, or twenty years before 
the invention of the threshing-machine, to which the Scotch 
millwright was the first to apply it. 
Three early inventors claim the introduction of the rotary 
straw-shaker, the next step in the development of the threshing- 
machine, viz. Gladstone, of Castle Douglas, 1794; Daily, of 
Northumberland, 1798 ; and Palmer, 1799 ; but there is reason 
to believe that, though not included in Meikle’s patent of 1788, 
rotary straw-shakers were used by him in some of his earliest 
machines. The modern straw-shaker dates from 1829 to 1837, 
there being two claimants for the invention, viz. Docker, of 
Findon, 1829 ; and Ritchie, of Melrose, 1837. 
In 1805, John Ball, of Norfolk, patented a machine, having 
a concave of iron bars and a drum, designed for simply sepa- 
rating the corn from the straw. This thresher rapidly became 
popular, especially in the Eastern and Northern counties, and 
was exhibited in large numbers at all the early Meetings of the 
Royal Agricultural Society, where it is now rarely seen, although 
still remaining popular in Ireland. 
A century has elapsed since Meikle’s day, but the threshing- 
machine is still an improvable piece of mechanism. The pro- 
portions of straw to ear, of ear to grain, of grain to chaff, the 
kind and quantity of weeds and foreign seeds in the crop, 
the dryness and consequent brittleness of straw and grain, the 
season of threshing, the age of the stack — these, and a thousand 
other minor conditions, differ enormously in every country, with 
ev^eiy season, and on every farm. Meanwhile, the threshing- 
machine maker depends for success entirely upon experiment, 
the application of theory to his work being out of the question. 
It is not surprising, therefore, that several generations of 
agi’icultural mechanicians should have passed away before the 
modern threshing-machine became as well correlated as it now 
