146 MECHANICS. 



It exhibits the apparatus by which the length of the 

 axle is altered to suit all kinds of planting ; by which 

 each hoe is kept independent of the others, so as to suit 

 the inequalities of the ground, and by which they can 

 be set any width, from seven inches to thirty. It 

 shows the oblique angle at which they run — this obliq- 

 uity being easily altered to any desired degree : this is 

 effected by a movement of the upper handle represent- 

 ed in the figure. By the lower handle the whole is 

 accurately guided. It is said that two men, one to lead 

 the horse, and the other to guide the implement, will 

 dress ten acres of root-crops in a single day, and that it 

 has proved eminently a labor-saving machine. 



CLOD-CRUSHERS. 



In clayey soils, clods are often formed in abundance 

 during the process of cultivation. These become very 

 hard in dry weather, and prevent the proper extension 

 of the fine roots of plants in search of nourishment, and 

 also the intermixture of manure with the soil, without 

 which it has been found that two thirds or even three 

 fourths of the value of manure is lost to growing crops. 



Different modes of pulverizing the clods have been 

 adopted. The simplest is the " drag-roller,'^'' repre- 

 sented in Fig. 124. It is made of a log or portion of 



Fig. 124. 



Clod-crusher. 



a hollow tree, into which a common two-horse wagon 



