1886. J FLAATATIOX PURPOSES. 555 



the last-mentioned and the minor, both as regards depth and width. 

 As far as possible, all openings into the main shonld be made in the 

 direction of the How of the water, not at right angles to it ; and 

 such openings, should they be necessary at both sides, ought not to 

 be formed opposite each other, but alternately. This, however, 

 is more important in dealing with covered drains. 



Fig. 1 represents what may l)e called " an area requiring drainage," 

 with a moderate and even slope, indicated by the dotted line FG, 

 and here the simplest and perhaps most generally employed com- 

 bination is that of a single main AB, cut at the base of the slope, in 

 conjunction with minors 013, DE, etc., falling into it at one side 

 only. In every case the outlet AH should have a decided fall, and 

 must be kept clear of weeds or other interruptions to the free egress 

 of the water. At the point or points where surface water leaves 

 the ground enclosed for planting, and enters covered drains, square 

 openings in the fence, formed of large stones or mason-work, should 

 be constructed. These should be supplied with strong gratings, not 

 imbedded in the stone, but hung upon pivots, or a few inches of 

 light chain : all danger of choking will thus be obviated. 



In Fig. 2 the heavy line represents a main drain cut along the 

 deepest part of a depression or hollow. Here again we have only to 

 deal with main and minor drains (the latter indicated by fine lines, 

 and the former by the heavy lines) ; but as we find rising ground 

 on both sides, a double set of minors becomes necessary, opening 

 alternately into the main. As in this case the fall at either side is 

 supposed to be but a slight one, they have been drawn at or near a 

 ri^ht angle to the main, as otherwise the incline would have been 

 insufficient for the proper discharge of the water. This brings them 

 into the main at right angles ; but the objection to this is modified, 

 or altogether obviated, by rounding off the outlets in the direction 

 of the flow of water in the main (as shown in plan), which will thus 

 assist in creating a current at the opening of each. 



Figs. 3 and 4 show instances in which, from the " lie " of the 

 ground, it is desirable to construct two main drains (again repre- 

 sented by broad lines) to receive the flow from a number of minors 

 laid up and down an even slope. In the former area thorough drain- 

 age has been judged necessary ; in the latter, only partial, those 

 parts remaining blank being considered sufficiently free from 

 moisture. 



In these cases, further explanation seems unnecessary. Attention 

 may, however, be called to a pair of the already mentioned spur 

 drains (see Fig. 4). 



We now come, for the first time, to deal with sub-main drains, 

 instances of which mav be seen in the two lines of medium breadth 



