TILLAGE MACHINERY 73 



water (holding it bottom side up) far enough to cool the 

 edge, then taking it out, and the color should be watched 

 as the heat returns to the edge. When a dark straw or 

 mottled purple reaches the edge, the entire share may be 

 cooled. 



Second. If a supply of oil is at hand, the share may 

 be tempered with less risk of breakage. When oil is used 

 (linseed or lard oil will answer) the share is to be heated 

 as before to a low cherry heat, then lowered into the oil 

 till entirely cool. After this it must be held over the fire 

 till the temper is sufficiently drawn, which will be indi- 

 cated by the oil on the thin part of the share taking fire. 

 It may finally be cooled by immersion in cold water. 



109. Draft of plows. The nature of soils, growth of 

 roots, and amount of moisture present influence the draft 

 of plows. The shape of the moldboard also affects the 

 draft, the more abrupt curvature producing a more pul- 

 verizing action upon the furrow slice, and requiring more 

 work. 



Professor J. W. Sanborn, of Missouri, made tests to 

 determine the reduction of draft due to the use of _a 

 coulter, the results of which are as here given. The tests 

 were made with a plow similar to the sod or breaking 

 plow, and in clover sod two years old, with about as 

 much moisture present as would permit working the soil 

 advantageously. The results were as follows : 



Total Draft 



Size of Furrow Draft per Sq. In. 



Sod plow with wheel coulter... 5.575" X 15.08" 296.25 3.524 

 " without " ... 5.325" X 14.5" 34375 4-453 



Difference 47-5O -9 2 9 



The coulter resulted in better work and diminished 

 the draft 20.86 per cent. A later series of observations 



