BAND AND COG WHEELS. 79 



iron on the lower side, which moves close to the ground, 

 below which a thin, broad coulter extends downward, 

 and to the lower end of this coulter a sharp iron cyhn- 

 der is attached. This moves horizontally, point fore- 

 most, through the soil, producing a hollow channel be- 

 neath the plow for the escape of the water, the only 

 trace on the surface being a narrow sht left by the 

 coulter. It is dragged forward by means of a chain 

 and capstan worked by a horse, the machine itself be- 

 ing fixed with strong iron anchors. This mode of 

 draining is only adapted to clay soil, and is very cheap- 

 ly performed, but is now little used since the introduc- 

 tion of tile -draining. Foivler^s Draining- Ploiv, de- 

 scribed hereafter, is a great improvement on the mole 

 plow, and draws the tile-tubing into the channel as 

 fast as it is made, forming a perfect drain by one op- 

 eration. 



BAND AND COG "WHEELS. 



Where great power is required, several wheels and 

 axles may be combined in a manner corresponding 

 with that of the compound system of levers already 

 explained. In this case the axis of one wheel acts on 

 the circumference of the next, producing a continued 

 slower motion, and increasing the power in a corre- 

 sponding degree. The wheels 

 are made thus to act by means 

 of cogs or teeth, or of bands 

 {Fig. 59). In ordinary prac- 

 tice, however, combined wheels 

 are made use of to multiply 

 Combined cog-wheels. motion instead of to diminish 



