26 JETHRO WOOD; 



screw auger ; and it has been likened to the 

 prow of a ship. Neither of these similitudes 

 conveys the fair and proper notion of the inven- 

 tion. 



" The mould-board, which the said Jethro 

 Wood claims as his own, and which is the 

 result of profound reflection and of numberless 

 experiments, is a sort of piano-curvilinear sur- 

 face, as herein-before stated, having the follow- 

 ing bearings and relations : A right line, 

 drawn by a chalked string or cord, or by a 

 straight rule, diagonally or obliquely upwards 

 and backwards from a point two inches and a 

 half inch above the tip or extremity of the 

 mould-board to the angle where the third and 

 fourth sides of the mould-board join, touches 

 the surface the whole distance, in an even and 

 uniform application, and leaves no sinking, 

 depression, hole, cavity, rising, lump, or pro- 

 tuberance, in any part of the distance. So, at 

 a distance half way between the diagonal line 



