1 Apri, 1902.) QuEENSLAND AGRICULTURAL JOURNAL. 239 
There is a special tool called a bottom-smoother (Fig. 7) for clearing 
out and preparing the bottom of the drain to receive the tile, and another 
(Fig. 8) is used for laying the tiles. Figs. 9 and 10 are for regulating the 
depth and width of the drain. 
11 12 
In Fig. 11 you have a draining-pipe, and Fig. 12 shows a section of the 
drain and the pipe lying in it. There is no absolute necessity to fit the tiles 
closely end to end, but they should always be laid even. Grass and rubble 
may be placed on top of the tiles before the earth is filled in. The total 
cost of tile drainage where carriage by rail or water is available is about 8s. 
per chain for tiles and 8s. 6d. per chain for digging, laying, and filling in. On 
the whole, tile-draining costs about £5 per acre. 
There is so much more to be said about drainage that it cannot be con- 
densed into this single lesson, so we will take a month’s holiday and resume 
the subject in the next lesson. 
Questions on Lesson 4. 
. What valuable soil constituents may be lost by drainage ? 
. Why should a leachy soil be covered with a crop ? 
. What is meant by the term “nitrification” ? 
. How does the open drain differ from the underground drain ? 
5. Describe the construction of the slab, stone, burnt earth, and tile 
drains ? 
6. What is the limit of efficient drainage in any soil? What is the 
general rule ? 
7. What size of tiles (diameter) should be used for lateral drains—(a) in 
stiff soils, (6) in open soils? 
8. What should be the diameter of tiles for the main drains ? 
9. How should tiles be laid ? 
10, What is the average cost of tile draining—(qa) per chain, (2) per acre ? 
He o> bo et 
Mr. J. W. Cartwright, Herbert River, has written to me on the subject of 
irrigation, of which I wrote in your 9th Lesson. I, of course, took Professor 
Storer’s figures as correct. I am much obliged to Mr. Cartwright for his 
correction, as I wish the lessons to be correct in every particular. This is 
what he says :— 
In the Agricultural Journal for January, page 7, “First Steps in 
Agriculture,” Lesson 9, 2nd Stage, it is printed that ‘ Professor Storer says 
[re irrigation] that [to give a hayfield a proper drenching] an amount of water 
is used which, if it were spread out evenly, would form a layer 4 inches deep 
