24 



THE GAEDENEE'S ASSISTANT. 



be formed, whilst the single tile (fig. 821) may 

 he sufficient for more or less of the upper part. 

 Fig. 822 is similar to fig. 820, but pipes are 

 used instead of tiles, and when covered with 

 9 inches or more of small rubble are much 

 the best form of small drains for a garden. 

 Fig. 823 is well adapted for a main drain, as 

 it allows a large quantity of water to pass. 

 The same may be said of the arrangement 

 seen in fig. 824, which affords a chance that 

 if roots get into one or even two of the 

 openings, still the third may be clear to act. 



Depth of Drains. — In many cases the depth 

 of the drains is limited by the outlet. Where 

 this allows of a sufficient fall, the top of the 

 materials forming the drain should not be 

 less than 3 feet below the surface, in order 

 that they may not interfere with deep trench- 

 ing, and that they may be further removed 

 from the danger of getting choked by the 

 roots of plants. Circumstances may render it 

 desirable that the drains should be cut to a 

 depth of 4 feet. 



Distance apart of Drains. — The distance at 



s 



Fig. 820. 



which drains should be formed depends on 

 various circumstances ; chiefly upon the porosity 

 of the soil or subsoil In stiff tenacious soils 

 the drains will require to be from 3 to 5 yards 

 apart, but in lighter soils they will draw well 

 at G to 8 yards asunder. If the depth of the 

 drains is 4 feet, and they are laid the above 

 distances apart, according to the tenacity or 

 porosity of the soil, they will generally afford 

 perfect drainage. 



Direction of Drains. — In level ground the di- 

 rection of the drain is, of course, determined 

 by the outlet, or by a main drain communicating 

 with some place of outfall. Where there are no 

 springs, and only the superfluous water of a wet 

 climate has to be drawn off, the drains should 

 run in the direction of the slope of the ground, 

 or slightly diagonal with it. If a Avatery stratum, 

 causing springs, has to be intercepted by a deep 

 drain, it ought to be cut more or less oblique to 

 the direction of the stratum; for by crossing 

 the slope of the stratum at right angles, the 

 drain would probably be level; or, if cut so as 

 to have a fall, part of its extent will be under 

 the stratum. 



In commencing the operation of cutting 

 drains, ohe outlets of the main drain should be, 

 if the declivity will permit, several inches above 

 the surface level of the water in the channel of 

 outfall. Drains on different sides of the same 

 channel of outfall should not enter it exactly 



\ I 



■ , 



Fig. 823. 



Fig. 824. 



opposite each other, nor should any drain be 

 led into the outfall, or into another drain, at 

 right angles. Although the general direction 

 of drains will often be at right angles to the 

 channel into which their water is discharged, yet 

 on approaching it they should form a gentle 

 curve in the direction of the stream or main 

 drain, so as to enter it at an acute angle. In 

 this way the two streams will unite and clear 

 away the mud that would otherwise accumulate 

 at the mouth of the drain. 



The small drains should have as much as 3 

 inches of a fall into the larger or main drains; 

 and more than this, for the general outfall, 

 would be desirable. It is a bad plan to termi- 

 nate the minor drains in an open ditch, as they 

 are apt to get choked. They should therefore 

 be made to fall into main drains, from which 

 the water will be discharged with greater force, 

 and thus keep their outlets clear. 



The main drains should be cut first. Then, 

 as soon as the lateral drains are cut, they should 

 be immediately laid, commencing the laying at 

 the top of the drain, or the place farthest from 

 the outfall, and terminating in the main drain, 

 with which each junction should be carefully 

 made. If the main consist of tile-pipes, there 

 should be branched ones for the junctions ; or if 

 not, a hole should be cut out in the side of a 

 main pipe, into which the terminating pipe of 

 the lateral drain ought to be neatly fitted. 



