To carry a watercourse over a canal, river, road, or railway, several methods may be employed, as, for example, by aqueducts like those of Arcueil and Buc near Versailles, and by upright and inverted siphons. Of these three means, the first is the most imposing, but is also very costly; and, besides, the declivities as well as the arrangement of the ground are not always adapted thereto. The inverted siphon is subject to obstruction and choking up in its most inaccessible parts, while the upright siphon is easy of inspection, taking apart, etc. But, _per contra_, the latter loses its priming very easily by reason of the formation of air spaces. [Illustration: FALCONETTI'S SIPHON.] Mr. Falconetti, an inspector of bridges and roadways, has found a means of rendering the latter occurrence impossible by an arrangement which is both simple and practical, and which is illustrated herewith. In the figure, a and b are the two vertical legs of the siphon, both of which enter the liquid. These open into the receptacles, c and d, in which the cocks, e and f, cut off or set up a communication with the pipes, a and b. These latter are connected by a branch, g, which may be put in communication with a reservoir, h, that is divided into two superposed compartments by a partition, i. Such communication may be established or cut off by a valve, j, maneuvered by a key, k, which traverses an aperture in the partition, i. Another aperture, m, in this same partition serves to put the two parts of the reservoir, h, in communication, and, for this purpose, is provided with a cock, n, which is easily maneuvered from the exterior. The object of this arrangement of cocks and reservoir is to prevent the siphon from losing its priming through the possible presence in the transverse portion of a certain quantity of air or gas that might be given off by the water and accumulate in this place. The compartment, A, of the reservoir, h, is designed for receiving the gases that collect in the top of the siphon, while the upper compartment contains water for making a hydraulic joint, and consequently preventing any re-entrance of air through the apertures in the partition, i. To prime the siphon, we shut the cocks, e and f, open the valves, j and m, and pour in water until the whole affair (siphon and reservoir) is full; then we close the cock, m, and open the three others. The siphon thus becomes primed, and begins to operate as soon as any water reaches one or the other of the lower receptacles. As the cock, j, is constantly turned on during the operation of the siphon, the air that has been able to accumulate in the lower compartment, A, of the reservoir, h, would finally unprime the siphon by intercepting communication between its two legs. In order to prevent such a thing from occurring, it suffices to expel the air, from time to time, that accumulates in the chamber, A, this being done, without stopping the operation of the siphon, as follows: