2258. The construction of the waterfall, where avowedly artificial, is nothing more than a strong-built wall across the stream, perfectly level at top, and with a strong, smooth, accurately fitted, and well jointed coping. On the perfection of the coping, both as to level and jointing, depends the regular distribution of the thin sheet of water to be projected. Formerly, artificial cascades of this sort were curved in the ground plan, the concavity pointing down the stream, by which some strength and a better view of the water were supposed to be obtained. With respect to strength, this can only hold true, or at least be of consequence, in cases where the upper slope of the dam is very steep, and the force of the current great; and as to a fuller view, this can only take place when the eye of the spectator is in the focus of the segment. Where a natural waterfall is to be imitated, the upright wall must be built of huge irregular blocks; the horizontal lamina of water broken in the same way, by placing fragments of rocks grouped here and there, so as to throw the whole into parts; and, as nature is never methodical, to form it as if in part a cascade.
