216 
IRRIGATION. — NO. L 
it remarked that, putting a weight on a cow's 
back would make her give her milk down. I 
accordingly drove her into the stable, got a 
bushel of grain and put it on her back ; but not 
being heavy enough, I took it off and put my 
elbows in the centre of her back, and bore on 
until she hollowed in her back. 
While she was kept in this position, she had 
no power to hold up her milk ; for it came down 
freely. After doing this a few times, and after- 
wards putting my hand on the back of the cow, 
it would give way, and she would immediately 
give down her milk. H. B. R. 
Huntington, L. I., May, 1850. 
IRRIGATION.— Wo. 1, 
Irrigation — Ground Plan. — Fig. 61. 
Irrigation, in a general sense, is applied to 
the watering of the earth by inundation, by 
sprinkling its surface, or moistening it by infil- 
tration, by means of rills or streams to increase 
its productiveness, The term, however, is usu- 
ally confined to the operation of causing water 
to flow over lands for nourishing plants. 
The artificial watering of the earth, chiefly to 
produce increased crops of grass, has been in 
use from a very early period. Frequent allu- 
sion is made to it in the Old Testament, and on 
the veracity of historians, we are led to believe 
that it has been practised by the Chinese and 
other oriental nations, as well as by the Mexi- 
cans ajid Peruvians, from time immemorial, In 
Italy, especially on the banks of the Po, the 
cultivators have certainly employed this pro- 
cess for a period previous to the days of Virgil, 
and it is still carried on with a zeal and care 
worthy of the art they practise. Cato, the ear- 
liest of the Roman writers upon agriculture, 
(150 years before Christ,) enjoined upon the 
Italian farmers " to make water meadows, if you 
have water, and if you have no water, have dry 
meadows." The directions of Columella, also, 
who wrote more than 1800 years ago, seem to 
have all the freshness about them of a modern 
age. He was the first who noticed the inferior 
nutrition afforded by the hay from water mead- 
ows. " Land," says he, " that is naturally rich, 
and is in good heart, does not need 
to have water let over it ; and it 
is better hay which nature, of 
its own accord, produces in a 
juicy soil, than what water draws 
from a soil that is overflowed. 
This, however, is a necessary 
practice when the poverty of the 
soil requires it; and a meadow 
may be formed either upon a 
stiff or free soil, though poor at 
the time water may be let over 
it ; neither a low field, with hol- 
lows, nor a field broken with 
steep rising ground is proper; 
the former, because it retains the 
water collected in the hollows too 
long ; the latter, because it makes 
the water run to quickly over it. 
A field, however, that has a 
moderate descent, may be made 
a meadow, whether it be rich, 
or so situated as to be watered ; 
but the best situation is where 
the surface is smooth and the 
descent so gentle as to prevent 
either showers or the rivers that 
overflow it, remaining too long; 
and, on the other hand, to allow 
the water that comes over it 
quickly to glide off; therefore, if 
in any part of the field intended 
for the meadow, a pool of water 
should stand, it must be let off by 
draining ; for the loss is equal 
either from too much water or 
too little grass." 
The whole art of irrigation may be deduced 
from the three following simple rules : — 
1. To free the land to be irrigated thoroughly 
of water, by draining. 
2. To give a sufficient supply of water dur- 
ing all the time the plants are growing. 
3. Never to allow the water to accumulate 
And remain sufficiently long on the land to 
stagnate. „ 
The general principle of irrigation, however, 
may be described as the supplying of every 
portion of the surface of the ground with an 
abundance of water, and taking it rapidly off 
again. In many localities, the great difficulty 
in irrigation arises from the want of a supply of 
water; but even then, a partial irrigation may 
