THE TRANSIT OF MERCURY.

Kumara Times, Issue 1595, 7 November 1881, Page 2

THE TRANSIT OF MERCURY.

To-morrow if the sky be clear or the sun unclouded between the hours of 10 a.m. and 3 p.m. New Zealanders will be favorably situated on the earth's surface for witnessing one of those occasional though rare interesting phenomena called a transit, being a transit of one of the two positively known planets, Mercury and Venus, whose orbits are between that of the earth and the sun. Such a phenomenon can only takfi place with these two planet--. The transits of Mercury over the sun's disc take place mote frequently than those of Venus, because the farmer is on fin average only 37 millions of inilos from the sun, whilst Venus is at an average distance of G 8 millions of miles from the great luminary of our .system. Whatever the weather may be (and 1-t us hope it will he. fair), a t 9.46 Kumara or New Zealand mean time tomorrow morning, the planet Meicury will commence a transit across the suu'a disc, when the following phases will occur :—The fir.-t external contact at ingress (that is, when the planet will first appear to touch the sun's (Use) will be at 9.4 G a.m : in two minutes from its first apparent contact with the sun the planet wiil ap;>e ; i" as a small round black spot, fairly on th-> sun's disc. This will occur at a few degrees south of the easternmost limb of the sun's disc. The planet will then appear to move gradually towards the centre of -the sun, when, at about. 27 minute.past. 1 2, it will be at its nearest approach to the sun's centre, passing the real ci-iitie at about one-eighth of ilie sun's

diameter. At G minutes past 2 Mercury will appear to touch the western limb of the sun, and in less than two minutes will pass completely off the sun's surface and become, invisible for many day.-, when in will again appear as a morning star, though too near the sun to he visible. After this there will not be another transit of Mercury till May, 1891 ; and this must be our apology for this loug notice. There will be a transit of Venus next year on the 7th December, but only the fiuish will be visible from New Zealand. It is, however, a much more important event for astronomers, for accurately determining the sun's distance from the earth j and another transit of Venus will not occur after that till 122 years have elapsed. It may be just possible to see the transit to-morrow with the naked eye, but a piece of yellow or smoked glass most be used to protect the eye. An opera-glass or telescope, also with a dark shade to protect the eye, is, however, necessary to have a good view of the phenomenon.