for carrying off all surplus water, and the leaves and rubbish brought down by it, before they reach the intake of your ponds. This is done by a side channel or by-wash of ample capacity. But perhaps the most common plan is to form a chain of ponds at the side of a brook from which the water supply is drawn, leaving the surplus water to pass off by the natural channel of the stream. In some situations it is a matter of great difficulty to get the water up, or the ponds down, to a suitable level for securing the necessary fall for a series of ponds. In such cases the services of a practical engineer may have to be called in; for it is impossible to devise a general scheme which would be well adapted to the peculiarities of each and every case. The proof of the pudding is in the eating; and, perfect as a system may appear on paper, it will be of no use unless it effectually secures your object, which is to ensure that the supply of water passing through the breeding ponds shall be constant and sufficient through all the vicissitudes of a fickle climate. In determining the number of fish a rearing-pond should hold, the size of the pond is of less importance than the minimum quantity of water which passes through it. But the temperature requires to be carefully observed, especially in the summer; and should the water show a tendency to become heated, the supply must be increased or you will run a serious risk of loss. To have complete control over the supply, and to be able to create an artificial 'spate' by sending down a flush of additional brook-water into your ponds whenever you think it desirable, is a very great advantage. The use of a Hornsby-Akroyd oil pumping-engine at the Weston Fishery, for the purpose of increasing at will the natural supply of brook-water during the hottest days of the summer, has been attended with great success. In respect to size, your ponds should be small for rearing purposes. 'When you mean business,' says Livingston Stone, 'build your ponds small; never let a trout escape to any place where you cannot get at it, observe it, and capture it at a moment's notice.' The shape of your rearing-ponds will depend upon circumstances; generally it is convenient to have them oblong. If the water supply is not very plentiful or cool the ponds should be deep and narrow, exposing a smaller surface to the rays of the sun. The quantity of water entering your ponds may be regulated by a hatch at the intake. In front of this is a sloping screen of perforated zinc designed to prevent the inlet from becoming clogged by leaves, weeds, and other floating matter collected and drawn against it. The outlet of a yearling pond should be so placed as to ensure free circulation for the current through the entire length and breadth of the pond. Two-year-olds require less current, but their ponds should be wider and deeper, although not necessarily longer than the yearling ponds. It must not, however, be forgotten that a wider pond exposes a larger surface to the sun's rays, and if there is danger of over-heating, shade must be provided. A convenient arrangement for a series of ponds is where they are separated by perpendicular dams or sluices formed by water-boards which slide into the grooves of a frame firmly fixed in a heading of brickwork, as shown in the illustration (fig. 16). By means of these boards the height of water in each pond can be easily regulated. To the topmost board of each sluice is attached a shoot of charred wood. To head up the water and increase the capacity of a pond you simply pull out the top board of the outlet sluice, and before replacing it insert an additional water-board of the required width. The outfall of each pond forms, as will be seen, a waterfall at the inlet of the pond immediately below it. The greater the fall from one pond to the other Р |