458 Effective Farming 



the screens, dust and chaff are blown away by an air blast 

 from a fan. The straw passes over racks to the stacker. 



230. Farm tractors. A statement about farm machinery 

 would be incomplete without mention of the modern farm trac- 

 tor. In recent years, these machines have been much per- 

 fected and are now used on many farms. For the most part 

 they are operated by gas engines, some form of petroleum being 

 the fuel employed. Many of them burn kerosene and gasolene 

 mixed; others burn only gasolene. Tractors can be secured 

 in a variety of sizes, from those that can pull one or .two plows 

 to those capable of pulling a dozen or more (Fig. 196). The 





FIG. 209. A tractor pulling six seeders. 



machines have many uses. In tillage work, -they often haul 

 plows and harrows at one operation. For planting, they can 

 be arranged to haul a number of seeders (Fig. 209). For 

 harvesting, they can be attached to a hay-loader (Fig. 59) or to 

 several mowers (Fig. 56), or to binders (Fig. 49), and a wide 

 swath can then be handled in one trip across the field. They 

 are useful not only for pulling loads, but the engines can also 

 be used to pump water, run the thresher (Fig. 210), saw wood, 

 and the like. Tractors are made in two general styles, those 

 with high wheels and those with a creeping tread. The latter 

 are especially useful on muck ground. In price the tractors 

 vary from a few hundred dollars to about $2500, the price 

 being governed by the size and power of the machine. 



