PLOUGH AND PLOUGHING. 



which follows the first, so as to stir 

 the subsoil without bringing it to the 

 surface. This idea has been im- 

 proved upon by constructing a sub- 

 soil plough of great strength, which 

 will go very deep into the ground, and 

 stir the subsoil a foot or more below 

 the bottom of the usual furrow. Mr. 

 Smith, of Deanstone, has invented 



one made entirely of iron {Fig. 22). 

 I'his plough requires four horses in 

 the most favourable soils, and six in 

 tenacious clays, to keep up with the 

 common plough, which always should 

 precede it. Many improvements have 

 been made on Mr. Smith's original 

 implement ; that represented in Fig' 

 urc 23 is one of the best : the three 



points cut down the earth gradually, 

 and pulverize it thoroughly. Some- 

 times, however, the subsoil plough 

 may be used alone, where the surface 

 is already mellow and crumbling. 



" Many different ploughs have been 

 invented for the purpose of saving la- 

 bour in draining land. See Draining 

 Plough. As they all cut out a slice 

 from the bottom of a furrow, and raise 

 it up to the surface of the ground, 

 they are of little use in crumbling 

 soils, and in the most tenacious re- 

 quire the assistance of much manual 

 labour to complete the work. They 

 act on the principle of the carpenter's 

 tool, by which a groove is formed in 

 Wie edge of planks or deals, when 

 they are intended to be joined close- 

 ly, as in a floor. This instrument is 

 also called a plough ; but the uniform 

 tenacity of the wood allows a narrow 

 chisel to cut an even, regular groove. 

 In the draining plough the two sides 

 of the drain are to be cut obliquely 

 downward and the bottom scooped 

 out evenly. The plough requires to 

 602 



be often adjusted, and the deep fur- 

 rows to be kept cleared from loose 

 earth by means of spades and scoops. 

 In this way drains may be made from 

 fifteen to eighteen inches deep, in 

 which loose stones or tiles may be 

 laid to form a channel for the water. 

 The expense is much less than when 

 the drains are made with the spade. 

 " A^'hen grass land lies low and wet 

 on a very tenacious subsoil, a plough 

 is sometimes used which consists of 

 a cylinder of iron pointed at one end, 

 and connected with a strong beam by 

 a thick plate of iron, which is sharp 

 on the side nearest the point of the 

 cylinder, and acts as a coulter. This 

 instrument is forcibly drawn horizon- 

 tally through the stiff subsoil at a 

 depth of twelve to eighteen inches, 

 so as to leave a round channel like 

 a pipe where the cylinder has pass- 

 ed. This has been called a mole 

 plough, the passage made by it under 

 ground resembling the workings of a 

 mole. It takes .six horses to draw 

 this plough when the cylinder is fif- 



