Zénith (balloon). The Zénith () was a hydrogen gas balloon of , designed by French aeronaut and navy officer Théodore Sivel, funded by the French Air Navigation Company () and built in 1874. The balloon set records before causing the first deaths of aeronauts due to altitude on April 15, 1875.

Construction 

Designed by Sivel, the Zénith was assembled and sewn at Pignet, Sivel's family estate, with the help of women from Sauve in the Gard department, in 1874.

Success of the Paris–Arcachon flight 

On March 23 and 24, 1875, under the guidance of Paul Bert, the commander Sivel, engineer Joseph Crocé-Spinelli, aeronauts Albert Tissandier, his brother Gaston Tissandier, editor-in-chief of the journal La Nature, and Claude Jobert achieved a long-duration flight (22 h 40), breaking all duration records. The balloon took off at 18:20 from Paris and landed the next day at 17:00 in Arcachon.

Departing from the gas plant of La Villette, Seine (present-day 159 , Paris), the landing took place in the commune of Lanton in the Gironde department. This flight led to numerous scientific observations, notably by Crocé-Spinelli in charge of spectroscopic observations, the Tissandier brothers studying the chemical composition of the air at high altitude, measuring the proportions of gases and water vapor in rarefied air, Sivel managing the balloon and assisting in his companions' experiments.

Ciron tragedy

Course of events 

After the balloon Zénith was inflated under the supervision of Adrien Duté-Poitevin, who was Sivel's brother-in-law, three aeronauts—Sivel, Crocé-Spinelli, and Gaston Tissandier—took off near the gas plant of La Villette, located in the 19th arrondissement of Paris, on April 15, 1875, at 11:35, hoping to break the altitude record ( at the time) and conduct observations.

Despite feeling unwell at  altitude, the three aeronauts decided to continue their ascent. Recorders showed that the flight reached . They all lost consciousness due to lack of oxygen (hypoxia). Only Tissandier managed to regain consciousness to slow the descent, and the balloon landed violently sometime after noon, tearing against a tree but with little damage to the basket, in the territory of Ciron (Indre) near Le Blanc,  from Paris, at 16:00. He alone survived – though he lost his hearing – and described his adventure and that of his companions in La Nature on May 1, 1875, and in L'Aéronaute the following month.

The tragedy was deemed unpreventable, as the effects of an altitude higher than  were unknown to the crew. Only the adventure of British aeronaut James Glaisher in 1862 could have given them any indication of high altitude conditions, but Glaisher had had training that allowed him to survive his flight. The Zénith did carry an emergency air supply consisting of three small rubber balloons containing 70 percent oxygen, but these were capable of sustaining breathing for an hour at most. Paul Bert wrote to the crew to warn them of the need to carry a larger oxygen supply, but his letter did not reach them in time.

The rapid ascent of the Zénith was also a significant factor in the incident. During World War I,  Gaston Tissandier's publisher Maurice Dreyfous wrote that the aeronaut had revealed certain details to him about the Zénith incident that he had previously hidden from the public. He said it was Sivel, and not Crocé-Spinelli, who was responsible for the sudden and deadly ascent of the balloon. He was supposed to constantly monitor the balloon's altitude with the barometer, but was a victim of his myopia and believed that the aerostat was about to touch the ground. He then threw overboard everything within his reach.

In all drawings of the incident, the actual shape of the Zénith basket was replaced by a square basket of less crude and more advantageous construction.

Impact and tributes 

The announcement of this incident had an impact in France and abroad, and more than twenty thousand people followed the funerals of Sivel and Crocé-Spinelli from the Orléans station to the Père Lachaise Cemetery in Paris.

Monument 

A public subscription was opened by the Société française de navigation aérienne to help the families of the victims and to erect a commemorative monument at the landing site of the balloon. It was designed by the architect Albert Tissandier (brother of Gaston Tissandier) and took the form of an obelisk in stone surrounded by a railing, on Rue de Eglise Saint-Georges in Ciron. Inaugurated on March 25, 1881, it was later listed as an historic monument by decree on April 4, 2017.

Performance halls 

French performance halls named Zénith owe their name to this balloon. In 1981, Jack Lang, then Minister of Culture, decided to create a large-capacity hall located outside cities, suitable for rock and popular music, and inaugurated the concept "Le Zénith" with the Zénith de Paris to replace the Pavillon de Paris. The first hall built was located in the Parc de la Villette at the take-off site, with the Minister of Culture being inspired by this feat to name the structure.

Tomb 

The remains of Joseph Crocé-Spinelli and Théodore Sivel were placed in a single tomb topped by their recumbent effigies lying on their backs, side by side with their hands intertwined. This ensemble, located in the Père Lachaise Cemetery in Paris (71st division), is an 1878 work of artist Alphonse Dumilatre.

Historical scene and music 

Musical scores (voice and instrument) for the theater were published shortly after the incident, such as those entitled Le Zénith (lyrics by Adolphe Perreau, music by Robert Planquette) or Les martyrs du Zénith, historical scene (lyrics by Julien Fauque, music by Jules Jacob), which remained on sale until 1901.

Poem 

This ascent and the resulting tragedy inspired a poem, named Le Zénith, by the French poet and future first Nobel Prize in Literature winner Sully Prudhomme.

See also 
 History of ballooning

References

Bibliography

External links 
 Martyrs made in the sky: the Zénith balloon tragedy and the construction of the French Third Republic's first scientific heroes by Patrick Luiz Sullivan De Oliveira
 Article on the record flight in La Nature 
 Complete article on the record flight in La Nature 
 The long-duration ascent of the balloon «Zénith», Gaston Tissandier, La Nature n° 97 - April 10, 1875 
 Article on the disaster in La Nature 

19th-century French experimental aircraft
1875 in France
Aviation accidents and incidents in France