146 POWER AND THE PLOW 



plow." He developed in theory and worked out in practice 

 both the vertical and transverse straight lines of the moldboard 

 which had been presented in theory by Timothy Pickering, and 

 by Thomas Jefferson in practice. He made a light iron plow, 

 on which the pressure of the furrow was evenly distributed 

 over the surface, so that the wear was equal on all parts. His 

 greatest contribution to progress, however, lay in the inter- 

 changeability of parts, so that a broken or wornout casting 

 might be replaced by any farmer. He thus instituted the era 

 of plow manufacture, as distinguished from that of plow build- 

 ing in small quantities by local carpenters, blacksmiths, and 

 plowwrights. To his everlasting credit it may be said that he 

 was instrumental in driving out of use thousands of the clumsy 

 "Bull" plows in existence. Sadly enough, Wood died a poor 

 man. He spent his fortune in protecting his patents. A grant 

 of $2000 to his heirs by the New York State Legislature was 

 the only substantial compensation growing out of his efforts 

 to improve the plow. William H. Seward, Lincoln's Secretary 

 of State, said: "No citizen of the United States has conferred 

 greater economical benefits on his country than Jethro Wood 

 none of her benefactors have been more inadequately 

 rewarded." 



Pickering noted that the soil, when adhesive, filled the 

 hollow of the moldboard and assumed a straight line from its 

 fore end, near the point of the share, to its upper projecting 

 hind corner, also that it maintained that same straight line. 

 This struck him as proof that this straight line should exist 

 in every moldboard as essential to the form giving the least 

 resistance. Said he: "No earth can be left on such a mold- 

 board; for every succeeding portion of earth which the plow 

 raises pushes off that which is on the transverse straight line 

 behind it; and the face of the moldboard consists is made up 

 (mathematically) of an infinite number of such transverse 

 straight lines." 



Edwin A. Stevens, in 1817, so shaped a moldboard that it 



