London, England/london5-035

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This is the spectral portion of interest that Lockyer observed. These are the spectral lines D1 and D2 (the double yellow lines of sodium) and the mysterious D3 line emanating from the sun, which was finally identified in 1895 as helium. Lockyer informally dubbed the new element "helium" for laboratory and informal conversations. He never used the name in print, however, because the element was only hypothetical -- some believed, for example, that it might be hydrogen under the unusual conditions prevailing on the sun. In publications he called the element "D3" because of its proximity of the bright yellow double lines D1 and D2 of sodium. Lockyer had no idea whether D3 might be a "metal like calcium or a gas like hydrogen" until the new element was discovered from terrestrial sources 27 years later and identified by Ramsay {LINK: London2D-80} and verified by Crookes {LINK: London6-300}. The spectrum had been observed by Jannsen {LINK: Paris6-230} two months earlier during a total eclipse in the sun in India, but Lockyer was the first to propose a the new spectral line was due to a new element.