Jan. 28, 1918 



Study of Plow Bottoms 



165 



This was accomplished by comparing the z coordinates of the bottom 

 ends of the pins with the distance which the plow had moved forward. 

 The distance which the plow moved forward is designated by s, so that 



s = vi, (47) 



where v = velocity of the plow, and i = time. 



By the use of the apparatus illustrated in Plate 9, A, the data given in 

 Table VII were obtained for the soil particles upon the bottom of the 

 furrow slice whose paths are shown in Plate 9, B. These data are typical 

 of 12 sets of observations. 



Table VII. — Values (in inches) of points in the furrow slice 



Unfortunately the soil available in the vicinity of Ithaca was not well 

 adapted for taking observations of the kind reported in Table VII. This 

 soil is not uniform in texture, contains many stones, cracks much more 

 readily than it stretches, and the surface is not as level as could be desired 

 for this work. At times it was difficult to drive the pins straight into 

 the ground. The data of Table VII show, however, a distinct tendency 

 for the difference between z and s to reach a maximum value and then 

 decrease again to zero; and also a slight tendency for this maximum 

 difference to decrease from Row I to Row V. When the work was begun, 

 it was hoped that sufficiently accurate data could be obtained from which 

 a law between z and s could be developed, but on account of the difficul- 

 ties already explained this was impossible. Consequently, in order to 

 develop a method for future work, a set of conditions were assumed which 

 agreed qualitatively with the observed facts. It should always be kept 

 in mind that this was done simply as an hypothesis whose exactness should 

 be thoroughly tested upon a soil better adapted to this work. The 

 conditions assumed for the relations between z and s are as follows : 



(A) That, for each path, when 2 = 40, 5 = 40. 



(B) That there was no stretching or compression in the outside bottom 

 edge of the furrow slice up to the point z = 40. 



(C) That the maximum difference, z—s, for Path I was 1.05 inches. 

 27807°— 18 2 



