62 POWER AND THE PLOW 



pump, or by a lubricator which feeds the oil by displacing it 

 with water. The former is preferable, as it eliminates danger 

 from freezing and is more economical and positive in its action. 

 On the cross-head, crankpin, and similar places a sight-feed 

 oil cup, feeding a rather thin oil by gravity, may be employed. 

 For lubrication of bearings, however, the tendency is to now 

 use grease cups and hard oil or greese, which is converted into 

 a fluid by the heat of friction. In the compression grease cup 

 the grease is forced on to the bearing by a plate and spring, or 

 by screwing down the cover of the cup. For lubrication of 

 the heavy gears axle grease is frequently employed, but since 

 this is apt to form a grinding paste with the dirt and sand which 

 are thrown up, means of washing the gears by a drip of thin 

 cheap oil are frequently employed. 



Modification of the Steam Plowing Tractor 



In some cases the traction wheels are made with removable 

 cleats, and an attachment provided whereby a drum can be 

 substituted for the front wheels, thus converting the engine 

 into a road roller. Some tractors may be equipped with an 

 attachment for running an elevator grader by the power of the 

 engine. A level gear on the countershaft drives through a 

 universal joint and telescopic shaft, doing away with loss 

 occasioned by the failure of the light grader wheels to provide 

 sufficient traction. English tractors equipped with cables 

 for pulling plows have already been mentioned. Some Ameri- 

 can tractors have a drum and short cable for pulling stumps 

 or lifting the engine out of difficulty. Others may be provided 

 with a derrick and cable to fit them for pulling stumps or for 

 steam-shovel work. Very interesting modifications of the 

 ordinary steam tractor are used in California in the soft re- 

 claimed tule lands. Some of these have drive- wheels and 

 extensions up to eighteen feet in width, and front wheels up to 

 eighteen feet wide, the entire tractor being forty to forty-five 



