Abstract
II. I HAVE already referred to the importance of applying in astronomical research the methods of the physicist. During the last quarter of a century the study of spectro-scopic phenomena in the laboratory has been completely transformed. It may well be said that this transformation, which has involved such discoveries as spectral series, the effect of pressure on wave-length, and the Zeeman effect, has been directly due to the use of Rowland's concave gratings, of great focal length, arranged for photography, in astronomical spectroscopy great advances have also been made, but the spectroscope has continued to occupy the place it formerly held as an attachment of the telescope. Although Rowland used a long-focus concave, grating for his classic study of the solar spectrum, the heliostat and Jens employed with this instrument gave so small a solar image on the slit that the investigation of sun-spots and other details was impossible. We thus see that while in the observatory the spectroscope continued to be used as an accessory of the telescope, in the laboratory the parts were exchanged and the telescope was employed simply as an accessory of the spectroscope. It seemed obvious that a great opportunity for advance lay open to the investigator owho would combine a long-focus spectroscope with a long-focus telescope. As it would be difficult, or perhaps impossible, to use for photography a sufficiently long spectroscope attached to the tube of an equatorially mounted telescope, some form of fixed telescope was plainly essential.
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Solar Vortices and Magnetic Fields . Nature 82, 50–53 (1909). https://doi.org/10.1038/082050a0
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DOI: https://doi.org/10.1038/082050a0