41G 
On Draiitiiif/. 
The above is a plan of the drainao;e of 13^ acres of land. The 
lines a a ... . show the parallel drains. The field is a piece of 
table-land, with but little fall into the ditches surrounding it, the 
highest part being, as shown by the dotted line c ; the main- 
drains B B, to obtain a greater fall, are carried through the fields 
adjoining (to which in their course they act also as main-drains) ; 
the other dotted lines show the old ridges, or the four different 
directions in which the field was always ploughed previous to 
being drained. Where the parallel drains empty into a main it 
is unnecessary to lay them through the headland. 
The ground being laid out as shown in Fig. 1, the space be- 
tween the minor drains will be 21 feet; depth from 28 to 36 inches ; 
the main and sub-main drains must be laid so that the bottom 
of the minor drains are on a level with the top of them. Where 
the old lands of a field lie in a proper direction for the fall of 
the main and minor drains, and their width is not less than 18 
nor more than 24 feet, it may, to save expense of labour, be con- 
sidered desirable to place the minor drains in the furrows, but 
for no other object. The operation of deep parallel under-drains, 
in conjunction with the atmosphere enlarging the fissures of the 
subsoil, is the most effectual in producing the free infiltralion of 
the water, and laying the land dry; as the bed of clay will contract 
near the drains as deep as the drains are laid ; and if they were 
laid a greater depth than is stated, the water would enter just as 
freely ; for though all the operations in agriculture should be 
conducted with relation to a judicious expenditure, it is better to 
err in laying the drains deeper than is necessary than too shallow, 
for where water lies in the fissures and worm-bores below the 
level of the conduit of the drain, it rises by capillary attraction, 
and expands the subsoil, which partially closing the fissures, 
worm-bores, &c., prevents in heavy falls of rain the rapid infil- 
tration of the water, thus causing it to flow over the surface to the 
furrows and flat parts, there to filter slowly through the deposit 
of mud on the surface, before it enters the fissures, 6cc., to perco- 
late to the drain. 
Some persons question if injury arises from water, not drawn 
off below shallow drains, rising by capillary attraction and expand- 
ing the subsoil; and also if such an agent exists: — a little 
reflection, and inquiry how it is that water poured into the pan of 
a common flower-pot so quickly ascends through the earth con- 
tained in it, will convince them that there is such an agent : 
and if they will take the trouble of filling two flower-pots wiiii 
earth, and into the pan of one pour water, the earth will retain 
the same appearance, but in the other the earth will contract, 
leaving a cavity round it. To some extent the same effect is pro- 
duced by water lying in the land below the conduits of shallow 
drains. 
