VIII. Determinations of wave-length from spectra obtained at the total solar eclipses of 1900, 1901 and 1905

Abstract

The following paper consists of a discussion of the photographs of the spectra of the chromosphere and corona obtained in three eclipse expeditions from the Royal Observatory, Greenwich. Preliminary reports of the expeditions of 1900 and 1905, where I was one of Sir William Christie’s party, are given in the ‘ Proceedings,’ vol. 67, p. 393, and A, vol. 77, p. 28, and a preliminary report of the expedition to Sumatra in 1901 is given by me in the ‘ Proceedings,’ vol. 69, p. 235. For these eclipse expeditions two spectroscopes were kindly lent by Major Hills, the same spectroscopes he used for photographing the chromosphere and corona at the Indian eclipse of 1898. Deference is made in the preliminary reports to the large amount of assistance received by voluntary helpers in these expeditions; for special assistance in the spectrographic observations I am greatly indebted to Mr. J. J. Atkinson, Mr. Arthur Berry, and Captain Brett. The spectrograms were measured at the Royal Observatory, Greenwich, by Mr. Davidson and myself, and I have profited by Mr. Davidson’s assistance and advice in the preliminary arrangement and adjustments of the spectroscopes as well as in the subsequent measurements and discussion. 1. Details of the observations and of the adjustments of the spectroscopes are given in the ‘ Proceedings,’ vols. 67, 69, and 77. The following is a brief account of the spectrograms of the chromosphere measured :—