“THE FORTHCOMING TRANSIT OF VENUS.”

Evening Star, Issue 3352, 17 November 1873, Page 3

“THE FORTHCOMING TRANSIT OF VENUS.”

To the Editor. Sir, —In an article bearing the above heading, which appeared in your last night’s issue, I notice one or two errors. The first is in reference to the time at which the transit of Venus will take place; and another is as to th« reason why New Zealand has been selected as one of the stations for observation. It is stated by the writer that the next transit “ will occur on the morning of Monday, Bth December, 1874.” Such is not the case. At Greenwich the transit will occur on tha morning of Wednesday, 9th December, 1874; the first external contact taking placeat 13h 45m 58s on the Bth December, astronomical time, which is lb 45m 58s a.m , or a little after a quarter to two o’clock on the morning of Wednesday, December 9, civil time. '• he last external contact take? place at Greenwich, December 8. 18h 26m 545, astronomical time, or at nearly twentyseven minutes past six on the morning o’ Wednesday, the 9th December, and both first and last contacts take place before sunrise. The transit is consequently invisible at Greenwich. The reason given by the writer why New Zealand has been selected as one of the stations for observation is ihat “ In northern latitudes the transit will just be over before a low December sun has risen above the horizon, so that observations, to be at all effective, must be taken from this quarter of the earth, where the sun will be considerably elevated during the four hours the planet will oecupyiug in cross ing the sun’s disc. On the morning of Sth December, the day on which the forthcoming trausit occurs, the sun rises in New Zealand at 4.38 a.m.” The writer seems to suppose that all places in northern latitudes are in positions similar to Greenwich. The fact, however, is that, not only is the most suitable station for observing situate in a high northern latitude, but that observations taken only in southern latitudes would be of comparatively little value. The sun’s rising at 38 minutes past four o’clock in the morning in New Zealand cannot have been a very important element in the selection of a station in this Colony, seeing that the transit begins and finishes in the afternoon of Wednesday, December 9, 1874. At Auckland, external contact at ingress will take place at about one minute earlier than local mean time, and at Dunedin at one minute later than local mean time. When the time of transit approaches nearer, I may perhaps trouble you with a further com* inundation on the subject.—l am, &c. A. H. Ross. Dunedin, November 15.