448 FUNDAMENTALS OF AGRICULTURE. 



the back side of the platform and sometimes upon the 

 ground. If too far back it does not grapple the grain 

 sufficiently to be of service, and if too far ahead it 

 does not give the grain sufficient momentum to cause 

 it to drop upon the canvas uniformly. The canvas 

 should be kept as tight as possible while in operation, 

 but should always be loosened when the machine is 

 to stand a few hours without working. The canvas 

 rollers should be parallel, and with their ends at right- 

 angles to each other. All the parts of the knotter 

 should be kept polished perfectly smooth and free 

 from rust. There should be no lost motion in these 

 parts no matter how slight it may be. If the knotter 

 pinion becomes worn it must be replaced by a new 

 one. The twine disk should be adjusted so that it 

 takes a force of about forty pounds to pull the twine 

 from it. If an untied band has a knot on one end 

 it is generally because the disk does not move far 

 enough, and the knotter-hook grasps only one cord. 

 Sometimes, however, this same trouble will occur when 

 the needle does not carry the twine far enough. In 

 that case the needle which is of malleable iron can be 

 bent. Always keep the knife perfectly smooth and 

 sharp. It is best to sharpen it with a fine whetstone 

 during every thirty or forty acres of cutting. 



Headers. In countries where there are large fields 

 and they are not too heavy, harvesters are used which 

 are known as headers or push machines. These head- 

 ers generally cut a swath about twelve feet wide, and 

 unless the machine has the binder attachment it ele- 

 vates the grain into a rack known as a header-box. 

 This header-box is on a wagon and is driven along 

 beside the header by means of an extra team. Four 

 or six horses are generally used upon push machines, 

 and they travel behind it pushing the machine before 

 them. 



4. Mowers. Such machinery as is used for gather- 

 ing the grasses can be called hay machinery. The first 

 of these is the mower which cuts the grass. The cut- 



