In both cases the sides of the gutter should be planted with quick-growing shrubs, and it will soon become ornamental. Such a slop-gutter on a raised and planted bank would form a most excellent boundary fence. These gutters are shown in figs. 26 and 27. The perforated tile which forms the floor of this gutter is a most important part of it, because it allows the gutter to be cleared of dead leaves and other rubbish, which inevitably fall into it, and it protects the porous material from getting clogged. It breaks the force of the water and prevents the downpour from the pipes from ploughing up the rubble, which is a most important matter. I have used various things for forming the floors of these gutters, and have found nothing better than the perforated tiles which are used for forming the floors of malt kilns. I have no doubt that the gutter could be made perfectly well in galvanised iron. What lengths of such gutters should be provided? To answer this question I can only give my own experiences. Two years ago I constructed such a gutter for a girls' school where there are between 30 and 40 day scholars and boarders. I dug out my trench leading into a natural rivulet, and I formed a gutter 40 feet long. I do not think the slops in this case have ever travelled as much as six feet, and there is no evidence that a drop of slop-water has ever touched the rivulet. The privets have grown, but the gutter has never been foul, and when the tiles have been taken up the porous rubbish beneath has been found perfectly sweet, and there has been no sloppiness at the sides. [Illustration: Fig. 27.—Filtration Gutter on Bank.] A similar gutter on a bank was provided for a six-roomed house, and the slop-water has never travelled to the end, or anywhere near it, notwithstanding a considerable fall. The water of a fixed bath has run for nine years into a gutter 20 feet long, and at times as much as 120 gallons a day has flowed into it, but the water is never visible two minutes after the waste has ceased to flow; there has been no foulness of any kind, and the only effect has been to make the shrubs grow. The bedroom slops of a country mansion with twenty-three inhabitants were taken, eighteen months ago, into a plantation, and the only result has been that the limes have thrown up suckers, but there has been neither sloppiness nor foulness. The bedroom slops of a cottage with five inhabitants have run for five or six years along a gutter 12 feet long, at the foot of a privet hedge, and there has been neither sloppiness nor foulness, except when, as stated above, I produced stagnation. _4. When it is feasible, it is advisable to allow different varieties of slops to flow in separate gutters._