124 FARM MACHINERY 



edge-selection drop-plate planter and claimed great accu- 

 racy for it. Varieties of corn differ very much in the 

 width of kernel, and for this reason provision has been 

 made by at least one manufacturer to vary the depth of 

 the edge-selection cell by substituting grooved bottoms 

 to the seed box over which the plate travels. A device is 

 provided with the flat plate for the same purpose. The 

 outside edge of the cell is made open, into which a 

 spring fits, excluding all but one kernel. 



170. Plate movement. Plates are made to revolve in 

 a horizontal plane, and also in a vertical plane. To plates 

 in these positions the names of horizontal plate and verti- 

 cal plate are given, respectively. 



The intermittent plate movement is one where the plate 

 is revolved until a hill is counted out, and then remains 

 at rest until put in motion for another hill by the check 

 wire. The movement may belong to full-hill or cumu- 

 lative drops. The argument is set forth that the seed cells 

 are filled to better advantage by this intermittent motion ; 

 the starting and stopping will shake the corn into the 

 cells. To cause the seed cells to fill more perfectly, the 

 kernels are prearranged by the corrugations and the slope 

 of the seed-box bottom. 



In the continuous plate movement the plates are driven 

 from the main axle usually by a chain and sprockets. 

 While the plates travel continuously, the size of the hill 

 is determined by a valve movement which opens and 

 closes the outlet from the seed plate. To produce this 

 movement, two clutches with double cam attachments, 

 one at each hopper, are used. At each trip of the planter 

 the dog on the clutch is thrown out, and it turns through 

 one-half revolution, allowing one cam to pass ; at the same 

 time the arm of the valve glides over the cam and opens 

 the outlet to the hopper, which allows the corn to drop from 



