142 



MECHANICS. 



together by hinges, so as to hend and fit an uneven 

 surface of land, and to he folded for carrying in a cart 

 or wagon. The dottted lines show the track of each 

 tooth. The Geddes Harrow, rep- 

 resented in Fig. 117, is supe- 

 rior to the square harrow on ac- 

 count of its drawing more stead- 

 ily from a centre, and its wedge- 

 form frame passing more freely 

 past any unusual obstruction. 

 To prevent the central part from 

 being lifted by the ^^'e-^ in- 

 draught, the draught- 

 Geddes Harrow. chaiu is fastcucd to the (j;-///j I K^\i 



side-beams, as in Fig. 118. ''''' hi >"'' 



The teeth of harrows are often made too large and 

 too few in number. Small and very numerous teeth 

 pulverize the soil more finely and rapidly. They 

 should be so placed that the corners, like wedges, 

 and not the sides, may cut the soil in their onward 

 progress ; and if the forward half of the teeth were 

 made sharp and flat, similar to the coulter of a plow, 

 they would not only run more easUy, but cut and pul- 

 verize clods more efficiently. This form of the teeth 

 would admit of the use of cast-iron, which would be 

 cheap and durable. 



The Norwegian Harrow., Fig. 119, is a new ma- 

 chine for pulverizing the soil, which performs the work 

 in a very perfect manner, by turning up instead of 

 packing down the earth. Two rows of star-shaped 

 tines play into each other, and produce a complete self- 



