102 



SPECIAL SUBSOILERS. 



on a kind of dray- 

 frame (Fig. 66). 

 The position of the 

 subsoiling discs with 

 regard to the wheels, 

 which are always in 

 contact with the soil, 

 is regulated by means 

 of a bent axle. The 

 discs are lowered or 

 raised by means of two 

 levers (one on each 

 side) 13 feet in length, 

 which can be clamped 

 Si on a ratchet sector. 



These levers might 

 ? be replaced with ad- 

 | vantage, by any device 

 | actually in use. The 

 ' depth of subsoiling 

 g may be modified, or 

 S the disc lifted out of 

 the ground altogether, 

 so as to turn at the end 

 of a furrow or for being 

 moved about. If only 

 one man is to lift the 

 discs, he has to act 

 upon each lever in 

 turn. In the experi- 

 ments one man took 

 one and a half minutes 

 to lift the discs, while 

 two, acting simultane- 

 ously, only took half a 

 minute. 



With a plough working to a depth of 12^ inches followed 

 by Thenard's digger (11 inches), the depth of cultivation 

 reached 23^ inches. 



At Baron Thenard's property, in fairly compact soil, three 

 good horses were required to pull a plough working to a 

 depth of 7 inches, the subsoil being very hard on account of 

 the prolonged drought of 1858. The digger required four 

 good horses to disturb the soil 1 1 inches deeper, but it was 



