Jan. 28, 1918 Study of Plow Bottoms 1 63 



to this same line of motion. The longitudinal rows are numbered from 

 II to VI (Row I was omitted because the colter upset the pins), and the 

 pins in each row numbered from i to 10, as shown in figure 11. When 

 the part of the furrow slice in which the pins were set was upon the mold- 

 board, it took the form shown in Plate 8, B. In order to obtain the 

 X, y, and z coordinates of points in the furrow slice upon the moldboard, 

 the apparatus shown in Plate 9, A, was used. In this apparatus the 

 axes have the same relation to the plow bottom as those shown in figure 

 8. This more detailed study of the furrow slice upon the moldboard 

 revealed the following: 



The length of Row II, pins i to 10, on top of the furrow slice was 

 greater than the length before the soil had passed upon the moldboard, 

 indicating that this por- 

 tion of the furrow slice yt 

 had been stretched. 



The length of Row 

 II, pins I to 10, was 

 greater upon the bot- 

 tom of the furrow slice 

 than its length before 

 the soil passed upon 

 the moldboard. 



The length of Row 

 VI, pins I to 10, on top 

 of the furrow slice was 

 less than its length be- 

 fore the soil passed upon the moldboard, indicating that this portion 

 of the furrow slice had been compressed. 



The length of Row VI, pins i to 10, on the bottom of the furrow slice 

 was greater than its length before the soil passed upon the moldboard. 



The lengths of Rows IV and V, pins i to 10, on top of the furrow slice 

 were approximately the same as their lengths before the soil passed upon 

 the plow bottom, indicating neither compression nor stretching. 



The lengths of Rows IV and V, pins i to 10, on the bottom of the 

 furrow slice was greater than their lengths before the soil had passed 

 upon the plow bottom. 



The z distances of pin 10 on top of the furrow slice were approximately 

 the same for each row, but less than the distance which the plow had 

 moved forward. 



The z distances of pin 10 on the bottom of the furrow slice were 

 approximately the same for each row and equal to the distance which 

 the plow had moved forward. (The coordinates of the pins at the 

 bottom of the furrow slice were measured by cutting away a portion 

 of the soil but leaving the pins in place.) 



Fig. 



