Light fountains - Expo Paris 1889

As night falls, the Exhibition fades into grey; half-tones extinguish the blues, the golds, the whites of the palaces, which become darker by the minute, profiling bastilles, minarets, a whole decor of bells and spires. Iron, in the indecision of twilight, becomes more artistic, erasing its modernism under false gothic allure, the openwork metal trusses seem like stone lace. It is the exquisite hour of the Exhibition; the softened bariolage of the costumes, the confusion of languages, less salient in the silence which gradually settles in the almost deserted palaces and gardens, as if for an entr'acte, all this semblance of contemplation removes the overly carnival note, the garish exterior of bazaar and caravanserai. It looks like a city of a future century, living from its normal, daily life, and no longer from the accidental, trampled, clashed assembly of all the arts, all the colours, all the races.

The Exhibition will rest. No... at the top of the Tower, a dull and trembling cord of light gives the signal: then the great lines of the palaces take shape in their turn, the dome shows its skeleton and finally the monumental fountain, at the top of the Garden which it feeds, the fountain surmounted by the heraldic vessel of Paris, the basin, the sprays of gushing water, an enormous one in the middle, with a procession of satellites, all this blazes and catches fire.

It is no longer water, it is a trickle, and it is also a thrust of coloured flames, straight, lying down, bending according to all the obliques, folding according to all the curves. Not the dead flames that painfully lick the firebrands of the braziers, but living, cheerful flames, shooting out strips of fire, to the right, to the left, up and down, up and down, like a clatter of light and colour...

Of colours... The flames were red, here they are blue, here they are green... here they are gold, here they are all white, simply virgin, terrifying like the final projection of a great fire when the fire triumphs and the last floors collapse.

Another will tell you some day here how these sprays of flame, these cascades of molten metal, are born, fed, handled. He will show you all the demons of this wonderful phantasmagoria. He will dismantle for you piece by piece this burning castel similar to those where the poets of the North lock up their captive Valkyries.

As for me, I only wanted to tell you how I saw the fairytale setting, how I felt it, how I admired it.

Our readers all know what a fairy-tale spectacle the blazing fountains and sprays of the basin in the central garden present in the evening. The monumental fountain surmounted by the vessel of the city of Paris no longer pours water, but cascades and sprays of flame into the large basin from which superbly coloured sprays spring.

Although not unprecedented, since the same thing has already been seen in Edinburgh and Glasgow, this spectacle is no less marvellous, and even more so if one considers the simplicity of the means by which it is obtained.

To operate the whole system of water and fire, three men are sufficient, one of whom is occupied only in directing the work.

If we examine the light fountains, we can see that all the jets can be reduced to two types, the vertical jets, and the parabolic jets; these two very different types each required its own lighting system. We will look at these two systems in turn.

For the vertical jets composing the large sheaf, established by Messrs Galloway and Sons, the isolated vertical jets and the small sheaves, the lighting is of marvellous simplicity. The water comes in through a very small nozzle, above a horizontal glass room, which is slightly above the usual water level in the basin. Below this room is a lighted focus with a reflector. There is therefore, next to each other, or better said one inside the other, a jet of light and a jet of water.

By virtue of a law of physics, which scientists call total refraction, all the light rays are absorbed by the water, enveloped in the liquid projection and up to the end of the jet, or better still, up to the last droplets which form as they fall back, the light remains trapped.

To tint this light, it is sufficient to interpose a coloured glass between the focus and the tile.

This is the general outline of the arrangement made by Galloway and Sons, on the one hand, and Sautter, Lemonnier and Company, on the other, for horizontal jets.
The two systems differ only in this respect: the horizontal electric fireplaces used by Messrs. Galloway and Sons are placed directly under the slab to be lit, through which their light is projected by a tin reflector, sufficiently indented to allow the ashes to escape. The foci placed by Messrs Sautter and Lemonnier are vertical. The reflector is a spherical mirror, made of silvered glass, and the original beam is therefore horizontal. But a plane mirror, inclined at 45°, is sufficient to reflect this light beam in the vertical direction.

All this, so simple to explain, forms in practice a considerable set of devices and arrangements, which had to be concealed, otherwise the whole illusion would be destroyed. It was necessary to show the spray of fire and not let the mechanics that provided it be seen. - This was achieved by having each spray emerge from a mass of cast iron reeds, which are so arranged and calculated as to cover the line of sight of the pipework, to the eye of a spectator placed in any situation. The parabolic jets have not been designed in such a way that the water and the light come out of the same opening, so that there is only one jet and all the machinery is hidden, but this does not simplify the interior layout, quite the contrary.

This arrangement is based on a physics experiment known as Colladon's. Contrary to the law governing the lighting of vertical jets, this experiment establishes total reflectivity. This law is quite clear and it is as follows:
If a stream of water is let out of a given vessel, through a narrow orifice and under a sufficiently strong pressure, this flow takes the form of a parabolic cord. If, on the other hand, a light focus has been arranged in such a way that its rays converge on the orifice, the liquid string will trap all its rays and keep them along its entire length.

However, "along the whole length" is only true within the limits of a laboratory experiment, and if we try to move into the realm of application, we soon find that whatever the intensity of the focus, there remains a fraction of the jet, the most considerable one, which does not participate in the illumination.
However, Mr. Bechmann, who worked on this system, found a solution which not only provides perfect illumination of the jet, but also allows considerable savings in the feed water. This solution consists of replacing the single nozzle by a double nozzle, formed by two trunks of cones fitted into each other, which produces not a liquid cord but an annular vein, the thickness of which could be reduced to 2 or 3 millimetres without letting the most intense light rays escape.
There is, as one can easily understand, a real water pipe through which the light ray passes. And curiously enough, when the pipe has first melted into a single jet and then separated into drops, the light continues to be retained by the liquid.

These are also flat mirrors, inclined at 45°, which send into the interior of the nozzle, the converging beams produced by horizontal electric foci, whose light can be coloured like that which illuminates the vertical jets.

This whole system of light colouring is gathered in groups, each of which can receive a different colouring. As there are five of these groups for the large spray and five for the other motifs, this gives a sum, so to speak, infinite of light effects, which can be produced at will by a team leader placed in a neighbouring kiosk from where he dominates the whole without being noticed by the public.

It is however he who is the real Deus ex machina of this fairy-tale setting. In his booth, he has a series of levers and electric buttons in front of him. The levers are used to operate the supply taps in the large sheaf and to vary the effects according to his inspiration. The knobs correspond to control panels, installed in chambers, which are located: one under the large sheaf, the other under the fountain.

In each of these chambers, a man, following the indications given to him by the board, operates the groups of coloured glasses placed under his control, by means of levers, the operation of which is very simple, as it is very similar to that of the needles on the railway lines. To guide himself, the worker reads on a board placed in front of him the indication of the manoeuvre to be carried out; and the movement indicated by the foreman, carried out by the levers, is immediately transmitted to the coloured glass systems.

The glasses can be operated separately or simultaneously. Thus, a violet colour can be obtained by interposing the two blue and red glasses between the projector and the jet.

Others are angled in such a way that the upper part of a jet can be coloured with one shade and the lower part with another. This produces truly magical effects.

No less than 300 horsepower are needed to supply the electricity required by the devices that illuminate the fountain and the sheaves. It is true that there are 48 of these devices and that the mass of water flowing out, which is used to make a mass of fire, is up to 1,200 cubic metres per hour, or 21,000 litres per minute.

If we consider that some of the jets are up to twenty metres high, we can see what a lot of light this represents, and we are astonished not by the force expended, but on the contrary by the little force required.

Nevertheless, the quantity of light supplied by the electric regulators is considerable, and the intensity of these foci is such that the worker in charge of operating them can only approach them by protecting his eyes with a black glass, without which he would inevitably be blinded.

©Livre d'Or de l'Exposition - Henri Anry.