THE PLOW IN AMERICA 



155 



moldboard plow for animal power where it seems impossible 

 to secure greater perfection. American plow-builders are 

 shipping their product by the millions annually to the newly 



Suction of the plow landward 



Suction of the plow downward. 



developing fields of Canada, Russia, the Argentine, to Mexico, 

 Spain, Australia, France, England, even to the cradle of the 

 modern plow Scotland itself. 



While the majority of inventors were devoting their atten- 

 tion to the moldboard plow, a few developed the disk plow, 

 largely with the idea of reducing the draft caused by the slid- 

 ing friction of the moldboard. In this they were only par- 

 tially successful, if at all, but they succeeded in producing a plow 

 which would work well under extreme conditions. Professor 

 Davidson, of Iowa State College, covers the essential consid- 

 erations thus: "In soils where the moldboard plow will do 

 good work there is nothing to be gained by the use of the disk 

 plow. The draft is often heavier for the amount of work done 

 and the plow itself is more clumsy than the other form. How- 

 ever, in sticky soils, where the moldboard will not scour, the 

 disk plow can often be made to do good work. Again, in very 

 hard ground, where it is impossible to plow with the mold- 



