Abstract
A LETTER from the Astronomer-Royal, in NATURE, vol. xviii. p. 380, giving the exact position of θ Cancri on the day of the total solar eclipse, intimates that, as the position given by Prof. Watson of the intra-Mercurial planet discovered on that day agrees so closely with that star, it may have been the object discovered, I have thought it advisable to give the facts concerning it, in order to correct such an impression if it still exists. That he had a view of the planet as stated there is no doubt, for I myself saw it some four or five minutes later, using θ as a comparison star, and am able not only to corroborate the discovery, but to substantiate the position given by him. Its proximity to θ enabled me to estimate its position with great exactness, especially in declination. It may be well here to state that I was prevented from searching to the east of the sun, in consequence of forgetting to untie a string with which I had tied, to the eye end of the telescope, a long pole to prevent the wind from shaking it, the end resting on the ground not allowing the instrument to be moved to the eastward. It is undoubtedly to this circumstance, which at the time seemed untoward, that I owe the discovery of Vulcan. In my eagerness to discover this hypothetical planet I had decided to ignore nearly all of the phenomena attending the eclipse, and as, at the commencement of total phase, there was visible neither the chromosphere nor any protuberances—nothing, in fact, but the corona, I almost immediately began the sweeps for it; but my hampered telescope behaved badly, and no regularity in the sweeps could be maintained. Almost at once my eye caught two red stars about 3° south-west of the sun, with large, round, and equally bright discs, which I estimated as of the fifth magnitude, appearing (this was my thought at the time) about as bright in the telescope as the pole star does to the naked eye. I then carefully noted their distances from the sun and from each other, and the direction in which they pointed, &c., and recorded them in my memory, where, to my mind's eye, they are still distinctly visible. I then swept southward, not daring to venture far to the west for fear I should be unable to get back again, and soon came upon two stars resembling in every particular the former two I had found, and, sighting along the outside of the tube, was surprised to find I was viewing the same objects. Again I observed them with the utmost care, and then recommenced my sweeps in another direction, but I soon had them again, and for the third time in the field. This was also the last, as a small cloud hindered a final leave-taking just before the end of totality, as I had intended. I saw no other stars besides these two, not even δ so close to the eastern limb of the sun. The distance between them was about 7′ or 8′.
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SWIFT, L. Discovery of Vulcan. Nature 18, 539 (1878). https://doi.org/10.1038/018539a0
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DOI: https://doi.org/10.1038/018539a0
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