Do you know what this drawing represents, which the artist has melancholically entitled: The Ruins, where we see a crumbling tower sitting on rocks covered with brambles and cythisis, and from which waterfalls flow, attracted by a lake that receives their tribute?
The engineer is hiding behind the painter. This represents the water tower of the Champ de Mars. It is from this ruined tower that the water pipes run that feed both the waterfall and the altered generators, which form sentinels around the Palace.
Look inside the tower and you will see a sheet metal tank four metres in diameter and five metres high. This tank is itself fed by powerful pumps located in two sheds on either side of the passageway under the Quai d'Orsay. There are five of these pumps, two in the upstream shed and three in the downstream shed. Each one of them would deserve a special examination, because each one is governed by a different system. But that would take us away from the goal we want to achieve, which is to explain the very complicated service of water distribution in the Champ de Mars.
By means of various pipes, these pumps draw water from the Seine, to send it, one to the lake placed under the lighthouse, the others to the reservoir of the Château-d'eau of which we spoke. They are assisted in this function by the powerful machines of the Friedland, built in the Indret shipyards and exhibited under the machinery shed of the French navy. The Friedland's machines provide free assistance, during certain hours of the day, to the suction pumps, which charge one cent per cubic metre of water raised.
For fear that the service thus organised might not be sufficient, and to prevent accidents, two calls for water from the city's pipes were made, one on Avenue de La Bourdonnaye, the other on Avenue de Lamotte-Piquet.
Do you think that this is all that was done for the water service in the Champ de Mars? Think again. We have only talked about what is called the low service. The pipes ordered for the Water Tower are only subject to the low pressure of 8m 00, i.e. less than one atmosphere, and can only serve the low parts of the Palace and the Park.
Let's talk about the high service, to which the main pipe of the low service connects in the direction of the Palace, which it circles by the circular ventilation gallery, to supply all the engines and all the needs of the Palace.
What is called the high service includes all the pipes fed by a special reservoir, built on the top of the Trocadero, at thirty-five metres above the ground level of the Champ de Mars. This height corresponds to a pressure of more than three atmospheres. The Trocadero reservoir, located close to the new boulevard Malakoff, has a capacity of 4000 cubic metres. It is itself fed by twenty-five horsepower elevating machines, installed on the bank of the left bank of the Seine, immediately downstream from the Iéna bridge. But, as a precaution against accidents which could stop the operation of the elevating machines, care was taken to provide a water intake directly from the city's pipes, as was also done for the lower service.
A forced water pipe starts from the factory, follows a canal cut in the entablature of the Iéna bridge, and goes up to the Trocadero reservoir, from where the stored water goes back down to the Champ de Mars through another pipe cut under the pavement of the bridge.
It is through this pipe that the water jets of the Palais and the Park, and the fire hydrants and sprinklers are supplied. Descending towards the Champ de Mars by the Pont d'Iéna, it crosses the entire length of the Palais with a diameter of 0.35m. At its meeting point with the large circular boulevard of the Park, it branches into a 0.25m pipe, which follows the entire perimeter of the avenue.
As it passes through the central garden of the Palais, it is further subdivided into pipes of 0.100 m in diameter, which radiate in all directions to supply the water jets and the numerous fire hydrants located inside the galleries, and then the sprinklers distributed in the Park.
The hydrants are superfluous, but what was necessary were the hydrants to preserve the immense riches contained in this palace of wonders. They were placed at the meeting point of all the circular aisles with the radiating cups; they were also placed externally under the covered walkway and even in the extensions of the radiating streets towards the Park, in order to facilitate the play of the pumps in case of accident.
Have such precautions been taken and such resources stored up in any previous exhibition? Waterfalls, lakes, jets of water, sprinklers and fire hydrants, supply of more than two hundred constructions in the Park; nothing like this had ever been planned or even imagined. If you lift the hatches of the machine gallery floor, you will find a real sheet of water underneath. It is marvellous! If this were all there was, the creation of the Champ de Mars would surpass anything we have seen.
As with the city of Paris, all the water pipes in the Champ de Mars are made of cast iron and laid on so-called ring joints, sealed with lead, which offers the immense advantage of being able to replace deteriorated pipes without being obliged to make long continuity solutions, as happens with socket pipes.
The laying of these innumerable pipes presented difficulties that the public hardly suspects. Studied at length and methodically prepared by Mr. Fournié, the work had to be undertaken in a very bad and rainy season. It took a great deal of skill and experience for the contractors to carry out the work in the midst of the embarrassments of the Palace and Park constructions, in freshly brought in soil that was constantly soaked by rain.
M. Mounot, head of section, directed the work on behalf of the Imperial Commission: the expense did not exceed 200,000 francs. This is why the water could be delivered to individuals at the price of ten centimes per cubic metre; that is to say, cheaper than in the city, and with no minimum consumption imposed.
The most real difficulty was the backflow under the pavement of the Pont d'Iéna for the double passage of the 0.35 m pipe which goes up to the Trocadero and comes down again. Mr. Vaudray, chief engineer of the Seine navigation, lent his active and intelligent support to this work.
We will speak another time about the filtered water service. The filtering is done instantaneously in a 0m,100 pipe which is sufficient for all the drinking water needs of the Palais and the Park, and for the supply of the aquariums.
The same exploration that we have undertaken for the water service, we should do again for the gas service. Everything will come in its own time; the road ahead is long.
It is good to inform the public of all that is being done at the Champ de Mars for their pleasure or satisfaction. This disclosure will serve as a lightning rod for its ingratitude, both within and beyond our borders. Justice has a slow pace and a lame foot; but it arrives nevertheless.
©L'Exposition Universelle de 1867 Illustrée