JANSSEN, (PIERRE). - OBSERVING SOLAR PROMINENCES.

Indication de quelques-uns des résultats obtenus à Cocanada, pendent l'éclipse du mois d'août dernier, et à la suite de cette éclipse. (Cocanada, 19 septembre 1868).

(Paris, Mallet-Bachelier), 1868. 4to. No wrappers. In: "Comptes Rendus Hebdomadaires des Séances de L'Academie des Sciences", Tome 67, No 17. Pp. (813-) 852. (Entire issue offered). Janssen's paper: pp. 838-839. A few minor brownspots.

First apperance of of the paper in which Janssen announced the first observations of a Solar Prominence without Eclipse.

"Janssen and Sir Norman Lockyer independently and about the same time discovered the method of observing solar prominences and the limb of the sun through using a high dispersion spectroscope in order to project the bright hydrogen lines of the prominence spectrum on the much attenuated background of the solar spectrum." (Shapley & Howarth "A Source Book in Astronomy", where this paper is translated on pp. 308-310).

"This (the spectra of helium in the sun) was announced on the same day by the French astronomer Janssen, who was in India observing a total eclipse. As a result, the French government some ten years later struck a medallion showing the heads of both scientists.
By that time, the two men had made a much more dramatic discovery at the same time, this time in cooperation. Janssen, studying the spectrum ofthe sun during the eclipse, had noted a fine line he did not recognize. he send a report on this to Lockyer, an acknowledges expert on solar spectra. Lockyer compared the reported position of the line with lines of known elements, concluding that it must belong to a yeat unknown element, possibly not even existing on the earth. He named the element, from the Greek word for the sun."(Asimov).

Parkinson "Breakthroughs" 1868 A.

Order-nr.: 51109