When, at an elevated point in a meadow, there exists a spring or vein of water that cannot be utilized at a distance, either because the supply is not sufficient, or because of the permeability of the soil, it becomes very advantageous to accumulate the water in a reservoir, which may be emptied from time to time through an aperture large enough to allow the water to flow in abundance over all parts of the field.
The storing up of the water permits of irrigating a much greater area of land, and has the advantage of allowing the watering to be effected intermittingly, this being better than if it were done continuously. But this mode of irrigating requires assiduous attention. It is necessary, in fact, when the reservoir is full, to go and raise the plug, wait till the water has flowed out, and then put in the plug again as accurately as possible - a thing that it is not always easy to do. The work is a continuous piece of drudgery, and takes just as much the longer to do in proportion as the reservoir is more distant from one's dwelling. In order to do away with this inconvenience, Mr. Giral, of Langogne (Lozere), has invented a sort of movable siphon that primes itself automatically, however small be the spring that feeds the reservoir in which it is placed. The apparatus (see figure) consists of an elbowed pipe, C A B D E, of galvanized iron, whose extremity, C, communicates with the outlet, R, where it is fixed by means of a piece of rubber of peculiar form that allows the other extremity, B D E, to revolve around the axis, K, while at the same time keeping the outlet pipe hermetically closed.
This rubber, whose lower extremity is bent back like the bell of a trumpet, forms a washer against which there is applied a galvanized iron ring that is fixed to the mouth of the outlet pipe by means of six small screws. This ring is provided with two studs which engage with two flexible thimbles, K and L, that are affixed to the siphon by four rivets. These studs and thimbles, as well as the screws, are likewise galvanized. Between the branches, A B D E, of the pipe there is soldered a sheet of galvanized iron, which forms isolatedly a receptacle or air-chamber, F, that contains at its upper part a small aperture, b, that remains always open, and, at its lower part, a copper screw-plug, d, and a galvanized hook, H.
In the interior of this chamber there is arranged a small leaden siphon, a b c, whose longer leg, a, passes through the bottom, where it is soldered, and whose shorter one, c, ends in close proximity to the bottom. Finally, a galvanized iron chain, G H, fixed at G to the bottom of the reservoir, and provided with a weight, P, of galvanized iron, is hooked at H to the siphon and allows it to rise more or less, according as it is given a greater or less length.
From what precedes, it will be seen that the outlet is entirely closed, so that, in order that the water may escape, it must pass into the pipe in the direction, E D B A C.
This granted, let us see how the apparatus works: In measure as the water rises in the reservoir, the siphon gradually loses weight, and its extremity, B D H, is finally lifted by the thrust, so that the entire affair revolves upon the studs, K, until the chain becomes taut. The apparatus then ceases to rise; but the water, ever continuing to rise, finally reaches the apex, b, of the smaller siphon, and, through it, enters the air chamber and fills it. The equilibrium being thus broken, the siphon descends to the bottom, becomes primed, and empties the reservoir. When the level of the water, in descending, is at the height of the small siphon, a b c, this latter, which is also primed, empties the chamber, F, in turn, so that, at the moment the large siphon loses its priming, the entire apparatus is in the same state that it was at first.
In short, when the water enters the reservoir, the siphon, movable upon its base, rises to the height at which it is desired that the flow shall take place. Being arrested at this point by the chain, it becomes primed, and sinks, and the water escapes. When the water is exhausted, the siphon rises anew in order to again sink; and this goes on as long as the period of irrigation lasts.
This apparatus, which is simple in its operation, and not very costly, is being employed with success for irrigating several meadows in the upper basin of the Allier. - Le Genie Civil.