Regulators are usually provided at all off-takes of branches. In the case of a channel taking off from another channel many times its own size there is generally only the head regulator of the smaller channel but in other cases there is a regulator in each channel below the bifurcation. Thus, when the number of bifurcating channels is two it is called a double regulator. Regulators, with the “falls”--introduced to flatten the gradients when the slope of the country is too steep--and drainage crossings and the bridges, provided at the principal roads, constitute the chief masonry works on a canal. At a fall, mills are often constructed or the fall may be used for electric power. Regarding curves and bends in channels, it is explained in _River and Canal Engineering_ that, as regards increased resistance to flow and consequent tendency to silt deposit, curves of fair radius have very little effect, that a curve of a given angle may perhaps have the same effect whether the radius is great or small but that if the radius is large a succession of curves cannot be got into a short length, that a succession of sharp curves in a short length may have great effect, amounting to an increase of N in Kutter’s co-efficient, that a single sharp curve has not much effect, that the chief objection to such a curve is the tendency to erosion of the bank, that at a place where the channel has, in any case, to be protected, as for instance just below a weir or fall, there is no objection to the introduction of a sharp bend and that such bends, in fact right-angled elbows, exist without any evil effects at many regulators when the whole supply is being turned into a branch. It is remarkable that on perennial canals no advantage is ever taken of the last mentioned fact. Cases undoubtedly occur, though somewhat infrequently, in which the most suitable and cheapest arrangement would be to give a canal an abrupt bend at a fall. In order to reduce eddying, the bend need not be an absolute elbow but can be made within the length of the pitching which would be curved instead of straight. This is frequently done on inundation canals, without the slightest drawback, even when there is no fall, the pitching at bridges being utilised. A pitched bend can be made anywhere. When a river floods the country along its banks as in parts of Egypt and of the Punjab, it is generally necessary to construct marginal embankments before irrigation can be introduced. The canal may take off at a point where flooding does not occur or it may pass through the embankment.[2] If it passes through at a point where flooding occurs, a masonry regulator is constructed to prevent the floods from enlarging the gap and breaking into the country. [2] For detailed accounts of such embankments and canals see _Punjab Rivers and Works_ (Spon) 1912.