In trimming these, or indeed any hedge intended as a close fence, they should be dressed up to a thin edge at top, as otherwise they are apt to get full of gaps below; and the cause is obvious, that the under part, in square or cut hedges, is too much shaded by the upper part. Now, by sloping the sides, every part of the hedge is freely exposed to the air; nor is any part over-dropped by another. A hedge, intended merely as a fence, need seldom be more than five feet high, or at most six. Screen hedges may be allowed to run to any height thought necessary for the purpose; neither is it requisite to trim them so often as fence-hedges; once a year, or in two years, may be sufficient. In the training of any hedge, it should not be topped or shortened, till it has arrived at a full yard in height; but it may then have a little taken off the points, in order to make it bush the better, and shoot afterwards of a more regular height; the sides, however, should be trimmed from the second or third year of planting, that it may grow the more complete and close below, for therein consists the excellence of any fence. It should not in topping, at any time while in training, be much cut in, as that would make it push the stronger to the top, to the detriment of the sides. When fence-hedges outgrow their limits, they must, of course, be cut either wholly or partly down; but if they be tolerably well kept, it is seldom necessary to cut them down more than half to the ground. 1097. _How to cut Box Edgings._--Box edgings should be cut about the beginning of April, or in the end of July. They should, however, be cut once a year, and should be kept two inches in breadth at bottom; being tapered up to a thin edge at top; for nothing looks so ill as a large, bushy edging, especially to a narrow walk. The use of edging is to separate the earth from the gravel; and the larger they are allowed to grow, the less effectual they become; getting the more open below, as they advance in height. Such also harbor snails, and other troublesome vermin. 1098. _A sure method of curing Gravel-Walks._--Three parts pond-water to one of brine, from the salting-tub in a family, poured with a watering-pot upon gravel-walks, will not only kill the moss upon them, but drive away the worms which make so many holes in them, and also prevent weeds springing up. This a gentleman lately tried, who has several gravel-walks in a grove near his house. Since he moistened his walks with brine--which is now four years ago--they are incommoded neither by moss, weeds, nor worms. Every autumn he causes them to be well watered with the brine and pond-water, during a whole week, to prevent moss; and a week in the spring, to guard against weeds and worms; besides giving them a sprinkling every now and then, in the summer-season, when they seem to want it.