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OUR ASTRONOMICAL COLUMN

    Abstract

    THE TRANSIT OF MERCURY.—Unfavourable weather appears to have very generally interfered with observations of the first contacts in the transit of May 6, in this country, and in France a similar adverse state of atmospheric conditions also prevailed. At Antwerp, Christiania, Göttingen, Josephstadt (Vienna), Kiel, and San Fernando (Cadiz), the contacts were observed and the results have been mostly published in the Astronomische Nachrichten. In two cases only is there any distinction made between what has been called geometrical contact, when Mercury appears perfectly round and his outer limb in coincidence with the sun's limb, and the instant when a fine filament of light is perceptible (or a connecting ligament is broken) which more correctly distinguishes the true internal contact. Thus at Kiel the time was noted when the planet appeared round and when the narrow luminous thread (deutlicher Lichtfaden) appeared. But the most complete observations of the first contacts hitherto printed are those made at the Observatory of San Fernando, near Cadiz, which are detailed in a circular issued on May 8, by Señor Cecilio Pujazon, the director of the establishment. Amongst the observers were Señores Garrido and La Flor, who had also experience in the case of the transit in November, 1868, at the same observatory, and with the same or very similar instruments, achromatics by Troughton and Simms of 80 mm. aperture. Three of the observers distinguish between what is termed “first internal contact” and separation of the limbs (desprendimiento de los limbos), the mean interval noted between the two phases being 18 seconds.

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