Willem Henri Julius

Willem Henri Julius (1860 to 1925) was a Dutch physicist who specialised in the study of solar radiation and related phenomena. A careful experimenter, he designed several instruments for the measurement of radiation. Born in Zutphen, the son of a school teacher of the same name, he studied at Gouda and entered the University of Utrecht in 1875. He became an assistant to C. H. D. Buys Ballot in 1882 and in 1888 wrote a doctoral dissertation on the spectra from flames and the vibrational frequencies of some gases. After teaching at Utrecht he joined the University of Amsterdam in 1890 and became a professor at Utrecht University in 1896. From his observations of the solar eclipse of 1901 he became immersed in solar radiation, examining anomalous scattering and explaining the increase in the redshift from the centre to the edge of the solar disk as dispersion by the solar atmosphere rather than the gravitational effect Einstein proposed.