History of the Plow. 21 



one behind; or, in other words, the forward coulter should have 

 the least rake, and the rear coulter the most. 



Fig. 17 is a coulter, a b; its length is two feet eight inches, e 

 d; its edge is sixteen inches long, d c; the length of its handle is 

 sixteen inches, one and seven-eighths inches broad, and seven- 

 eighths inch thick. 



Fig. 18 is a nut with its two opposite corners turned up so as 

 to be driven by a hammer. 



Fig. 19 is an iron collar (bridle) by which the tow chain is 

 fastened to the beam, as seen at a, fig. 3. The notches are in- 

 tended to facilitate the direction of the share to or from land. 

 The length ot each side of this collar is one foot. 



The tow chain is shown in fig, 3, where the link Y is secured 

 by the stake, as shown in fig. 1. 



Fig. 20 is the iron wilds. The distance between the two legs 

 is eight and a half inches; their length is nineteen inches. Its 

 position is seen in figs. 1 and 2; the notches are intended to give 

 a broader or narrower furrow. E is the ring by which the two 

 links and the two crooks, F and G, are held together, and on 

 which they all move. 



The diameter of the left wheel in fig. 2 is twenty inches; of the 

 right, two feet three inches; their distance asunder is two feet 

 five and a half inches. 



The crow staves are one foot eleven inches high from the box 

 to the gallows, and their distance apart is ten inches. The height 

 from the plane of the sole to the hole in the box where the tow 

 chain passes through it, is thirteen inches, which is two inches 

 below the holes of the wilds on the rear face of the box. The 

 height at the other end, where the crook of the collar takes hold 

 of the pin of the beam at c, fig. 2, is twenty inches high. 



No other noticeable changes were made in the plow until 

 near the beginning of the present century, when the conviction 

 that there was a real law of nature which ought to regulate the 

 shape of the plow, began in a vague and misty way to take pos- 

 session of men's minds. They felt instinctively that the imple- 

 ment was too complicated and cumbrous, and that it was quite 

 possible to simplify it and to diminish its draft. 



One of the earliest laborers in this field was Thomas Jefferson, 

 late President of the United States, who, in a communication to 

 the French Institute, attempted to solve the mathematical problem 



