Oeuvres de Jules César (French Edition)

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Write a customer review. Amazon Giveaway allows you to run promotional giveaways in order to create buzz, reward your audience, and attract new followers and customers. Learn more about Amazon Giveaway. Set up a giveaway. There's a problem loading this menu right now. Learn more about Amazon Prime. Get fast, free shipping with Amazon Prime. Get to Know Us. English Choose a language for shopping. The brightness of the rays led Janssen to suspect the possibility of observing the prominences even when there was no eclipse. The next day he resumed his observation of the solar limb, admitting only the red portion of the spectrum.

He ascertained first that a bright line appeared in the exact extension of a dark line of the solar spectrum, the C ray.

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Exploring the contour of the sun, Janssen observed the variations in the intensity of the line and the modifications in its structure. He also made other bright lines appear, all of them corresponding exactly to the dark lines of the absorption spectrum. From 18 August to 4 September Janssen worked on establishing maps of prominences. He continued his observations at Simla, in the Himalayas. On 25 December he wrote that the solar photosphere is surrounded.

Several other astronomers worked in these areas during this period, notably Lockyer, who arrived at the same method of analyzing the prominences as Janssen did; but it was the latter who, in the course of his stay at Simla, created the first spectrohelioscope. He described the essential device of this apparatus as follows:.

For carrying out his investigations Janssen received official subsidies at the times of his missions.

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Yet, in France at least, he had little more than his home to use for his technical and experimental work. In the minister of education, Victor Duruy, tried to find him an observatory. Janssen had had the opportunity to make several measurements at the Paris observatory but was not able to intall himself there permanently, since the director, Le Verrier, considered the establishment to be his personal property.

In the French government decided to establish an observatory for physical astronomy. Janssen had the choice of two sites: Malmaison the former residence of Empress Josephine or Meudon, better located in terms of climate.

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Janssen chose Meudon and it was granted to him in The estate at Meudon was in ruins when Janssen moved there in October He commenced repairs on the buildings and began to prepare the astronomical equipment. The offices and laboratories were lodged in the principal part of the estate, which formerly consisted of a modest chateau, stables, and other outbuildings.

A separate building, the Chateau Neuf, built by Mansart in , was restored and topped by an astronomical dome Janssen had hoped he would rapidly acquire the means necessary to extend his investigations, which until then he had conducted with small instruments and improvised devices. Soon, however, there were financial difficulties.

It became necessary to use funds budgeted for research for the completion of the buildings, a task that required twenty years. The staff was insufficient moreover—until there were only two astronomers. Nevertheless Janssen was able to endow the observatory with two large instruments: For the spectral investigation of gases, he also set up a large laboratory with a steel tube sixty meters long, closed by thin transparent plates and capable of supporting a pressure of atmospheres.

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Composed of a selection of exposures made between and , it summarized the history of the surface of the sun during these years. Janssen employed a photoheliograph of his own design. It was not possible to make all the solar observations at Meudon. Janssen was well aware of the advantages of observing at high altitudes. His age and his lameness did not allow him to make the climb on foot, especially at that season.

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Thus he invented a conveyance to be borne by porters. It consisted of a seat fixed under a horizontal ladder: The ascent, which lasted thirteen hours, was as exhausting for Janssen as for his porters. But the instruments were installed immediately; and the observations, which he was able to make during the whole of the third day, were sufficient to provide a solution to the problem under study. The dark rays were either nonexistent or so weak that it could be deduced that they would not exist for an observer at the limit of the terrestrial atmosphere.

Encouraged by this experiment, Janssen repeated it in , this time at the summit of Mont Blanc 4, meters. The measurements confirmed the earlier results. Despite the difficulties encountered the caravan left Chamonix on 17 August but did not arrive at the summit until 22 August , Janssen decided to erect an observatory there for conducting studies in physical astronomy, terrestrial physics, and meteorology. By July he had gathered the necessary funds and equipment, and two years later the observatory was completed.

The initial stages were completed at Meudon, where a fifteen-ton building had been set up, which was then transported to Mont Blanc in pieces. Each piece had to weigh less than thirty kilograms so that it could be carried by porter to the summit. Although his observatory did not withstand the rigors of the weather, Janssen had set a splendid example by his energy and unfailing courage. In the annual Mont Blanc expedition set out to determine the solar constant. Janssen had broken a leg on the staircase of the large dome at Meudon and was unable to manage the climb.