OPERATIONS OF TILLAGE. 147 



bars, and to the line of the harrow's motion, and the teeth 

 are inserted into them at equal distances from each other. 

 This inclination is made to be such, that perpendiculars 

 falling from each of the teeth upon a line L M, drawn at 

 right angles to the harrow's motion, shall divide the space 

 between the bars into equal parts, so that the various 

 teeth, when the instrument is moved forward, shall indent 

 at equal distances the surface of the ground over which 

 they pass. 



" The number of teeth in each harrow is twenty, five 

 being inserted in each of the larger bars. When two 

 harrows, therefore, are employed together, the surface of 

 the ground from L to M is indented by 40 teeth, impres- 

 sing the ground at equal distances from each other, and 

 covering the space of about 9 feet. The teeth may pro- 

 ject below the under surface of the frame 7 or 8 inches, 

 their length somewhat increasing from the hindmost to the 

 foremost rows, where the oblique position of the line of 

 draught tends most to elevate the harrow. The teeth 

 are often inserted into the frame with a little inclination 

 forward ; but this deviation from the perpendicular, if 

 made at all, should be very slight, because it renders the 

 harrow more apt to be impeded by the weeds or oth- 

 er substances collecting in the angle between them and 

 the frame. The teeth are fixed in the bars by boring 

 holes with an auger of about f of an inch in diameter, 

 and then drawing them firmly through. The teeth, when 

 thus driven into the bars, will be retained with sufficient 

 firmness. The best of the common kinds of wood for 

 the larger bars, as being least liable to split, are elm, beach, 

 or ash, and for the cross-bars ash. 



" The iron rods which terminate in the hinges, O, O, 

 may pass through the frame-work, to give it greater 

 strength. These rods keep the harrows at the distance 

 required, and the hinges admit of either harrow rising or 

 falling according to the inequalities of the surface. When 

 thus joined, the harrows are drawn by two horses guided 

 by reins, the driver walking behind, so as to be prepared 

 to lift up either harrow when choked by weeds, or other- 

 wise interrupted. 



