142 TECHNOLOGY. 
ploughing is, the destruction of weeds, which are turned under with the 
surface soil, and covered with the layer immediately beneath it, which is 
brought up in contact with the atmosphere and laid in narrow parallel 
ridges. This turning up and separating from the subsoil is performed by a 
sharp horizontal plate of iron called the share ; the dividing into narrow 
ridges is the work of a vertical iron called the coulter ; and the turning over 
is done by a board shaped for the purpose, called the mowld-board. Every 
plough consists of these three elements, arranged in proper order, the 
coulter preceding the share and mould-board. Ploughs may be divided into 
two great classes: those with wheels, called wheel-ploughs, and those with- 
out, called swing-ploughs. _ 
In pl. 29 ploughs of different construction and for various purposes are 
represented. 2g. 1 is a swing-plough in use in Belgium, the share and 
mould-board of cast-iron, and forming an uninterrupted and continuous 
eurve ; jig. 2 is a Brabant plough, also of cast-iron, which runs very steadily 
and may be set to cut deep or shallow, narrow or wide furrows ; jig. 3 is a 
Flanders cultivating plough ; jig. 4 is a Belgian plough, used for breaking 
up sod-land ; jig. 5 is a Bohemian plough ; jig. 6 is a form of subsoil plough 
or deepener, for increasing the depth of the soil and moving the subsoil ; jig. 
7 is a shovel plough, for cultivating growing crops; jig. 8 is a small plough, 
used also for cultivating and hilling potatoes and other crops; jig. 9 repre- 
sents a plough so arranged as to keep the furrows without the aid of the 
ploughman ; fig. 10 is an old Thuringian plough; jig. 11 is the so-called 
ehampion plough, with the guide wheels of unequal diameter, the right 
wheel running in the furrows ; jigs. 12 and 13 are right and left hand views 
of a German plough, which nearly resembles the Belgian; jig. 14 is a 
simple form of subsoil plough, which breaks up the subsoil without bring- 
ing it to the surface; jig. 15 is a hand plough, for working between the 
rows of seed beds; jig. 16 is a plough with wheels behind the sole, to 
diminish the friction upon the subsoil; jig. 17 is a light plough, used for 
covering stubble before winter. | 
In no part of the world, perhaps, have the mechanics of agriculture made 
such rapid advancement as in the United States. The plough has been 
made much lighter and of easier draught, whilst its cost has been materially 
lessened. Amongst others an ingenious instrument has been invented for 
digging potatoes, which promises to be a great labor-saving machine. Im- 
provements have also been made in ploughs for cultivating upon the sides 
of hills, and in the common cultivator. 
2. Tue Harrow. The object of the harrow is three-fold : more completely 
to pulverize the ground after it is left by the plough, to eradicate and destroy 
the roots of weeds and grass, and to cover seed when sown broad-cast. It 
consists of a strong wooden frame filled with wooden or iron pins, each of 
which as the harrow is moved makes a small furrow, or breaks the clods it 
may encounter. 
Pil. 29, figs. 18 and 19, are old forms of the Scotch harrow, with hori- 
zontal and oblique teeth; jig. 20 is a harrow with hooked teeth, for the 
purpose of eradicating weeds and grass; jig. 21 is a form of cultivating 
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