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1 May, 1902.] QUEENSLAND AGRICULTURAL JOURNAL. 317 
4, What precaution must be taken when starting the minor drains, at their 
opening into the main drain? 
| 5. How would you drain a swamp on rising ground and a steep hill 
slope ? 
: 6. If your paddock is longer than 200 yards, what course would you adopt 
to make all the drains effective ? 
7. Why should drains not be at once filled in on soft spongy land ? 
8. Give two examples showing that it pays to drain wet land. 
THIRD STAGE. 
7ru Lisson. 
IRRIGATION. 
Having your farm properly drained, you may now think of another very 
important matter—a regular supply of moisture to the crops. Although crops 
on drained land can stand a dry spell much longer than those on undrained 
land, still, unless a certain and regular amount of water can be supplied to the 
plants, the best results are not to be expected. Although throughout a period 
of forty-two years the mean annual rainfall in Queensland has been 50°37 
inches, with an average during that period of 133 wet days in the year, still 
this rain water is unequally distributed. The North and the coast lands get a 
fair share, as a rule, but the Western country is alternately flooded or dried up 
by drought. 
If you refer to Lesson 9 in the Second Book you will find that I gave you 
the quantity of water contained in every 100 lb. of vegetables, grass, grain- 
plants in blossom, and in 100 lb. of mature leaves of trees. 
One inch of rain is equal to 4°673, or a little over 44 gallons of water to 
the square yard, or 22,617 (101 tons by weight) to the acre, so that a much 
smaller rainfall than that of this State would supply an immense quantity of 
water to each acre. But, as I have already said, the rainfall is unequally 
distributed both as to seasons and districts, and in spite of the fairly sufficient 
amount of cloud water there will be times when your crops will languish or fail 
altogether, because the rain did not come at the exact time when the plants 
required it. ¥ 
How are you to regulate the water supply so that the crops will get all the 
water they require during the whole growing season ? 
By irrigation. (Look up Lesson 9 again in Book 2.) You have probably 
read or heard of the great River Nile in Egypt, which every year in the 
same season regularly overflows its banks, spreading out far over the land on 
either bank. This overflowing is anxiously looked for by the Egyptian farmers, 
for they depend entirely upon this water, and the rich sediment it leaves 
behind, to produce those magnificent crops of cotton, cereals, and many other 
farm products for which that otherwise sandy, arid country is celebrated. 
~ Millions of acres of sandy desert in Algeria, and in other parts of Northern 
Africa, have been changed into rich fertile fields, simply by irrigation works of 
great magnitude. I cannot here describe them to you, but you can find out all 
about it from other books. 
The amount of water required to give a field a good drenching would, if it 
were evenly spread over the surface, lie 4inches deep all over the field. That is 
the calculation by many scientific men, whose figures it is that I give you here. 
They say that half of this sinks into the soil, and the other half flows off, and 
is utilised on fields lying at a lower level. The amount of water delivered on to 
a field is measured by cubic feet—so many cubic feet a second. 
Of course you know what a cubic foot is, but, in ease there should be any 
of you who do not know, a cubic foot is a figure (rectangular), which 
measures a foot every way, in height, length, and breadth. If you make a box of 
those dimensions inside, and fill it with water, you have a cubic foot of water. 
Before you can irrigate, however, you require two things. One of these is 
water, of course, and the other is some means of getting it cheaply and easily 
onto the land. Now, you may at once give up the idea of irrigation if your 
