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:
After closing the cock, j, water is poured into the reservoir, and,
running down to the lower compartment, drives out the air through the
cock, m. This operation once effected, it only remains to turn off the
cock, m, again, and open j in order to establish the normal operation.
As the chamber, A, is provided externally with a water gauge, N, it may
be seen at a glance when it is necessary to maneuver the cocks in order
to expel the air.
This system of siphon is evidently applicable to all sorts of liquids.
It may likewise undergo a few modifications in its construction; for
example, the valve, which in our engraving is placed over the siphon,
may be located at any distance from the apparatus, although it should,
in all cases, be in constant communication with it by means of a tube,
and be placed a little higher than the siphon. It may then be put under
cover and be kept constantly in sight, thus greatly facilitating its
surveillance.
As may be seen, the essential peculiarity of this improvement consists
in the very ingenious arrangement that permits of immersing the cocks in
the liquid to make them perfectly tight, it being necessary that they
should be hermetically closed in order to prevent the entrance of air
to the siphon. Everything leads to the belief, then, that if upright
siphons have never been able to operate regularly, it has been because
no means have been known of expelling the air from the interior without
letting air from the exterior enter at the same time. The arrangement
devised by Mr. Falconetti gets over the difficulty in a very elegant
manner. It seems as if it would be called upon to render great services
in the industries, and it well merits the attention of engineers
of roads and bridges, and of contractors on public works.--_Revue
Industrielle_.
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