TO CORRESPONDENTS.

Kumara Times, Issue 1565, 3 October 1881, Page 2

TO CORRESPONDENTS.

W. R., Greyraouth.—(l.) The Penny Cyclopaedia (English, we suppose you refer to) would be right in saying the transit of Mercury is to take place on the 7th November; lOh. 16m. p.m. being .Greenwich time at which it commences. But as in England* the sun sets on that day at 4.21 p.m., the sun will be 60° below the horizon of Greenwich when the transit commences, and therefore it will be invisible to observers in Europe. As we are nearly at the antipodes as regards Greenwich (the mean being calculated at ll£ hours for all New Zealand astronomical observations), it will be obvious from the foregoing considerations that the transit must take place when the sun is above our horizon ; and as our position is, in longitude, east of Greenwich, it follows also that wo are so much (ll£ hours) in advance of Greenwich time. To make short, 10.16 p.m. Nov. 7th, in England, corresponds in time to 9.46 a.m. Nov. Bth, New Zealand. The external contact of the planet Mercury with the sun will take place at 9.46 a.m. November Bth ; the internal contact at ingress at 9.48 a.m. At about 20 minutes past 12 the planet will appear almost in the centre of the sun’s disc. The internal contact at egress will take place at 3.6 p.m.; and the planet will disappear off the sun’s disc at 3.8 p.m, (2.) Almost any geography will explain the tides ; but certainly any book on astronomy. (3.) The moon rotates upon her axis in exactly the same interval that she requires to perform n revolution round the earth, which is 29 days 12 hours 44 minutes 3 seconds ; in consequence of this she always presents the same side of her surfivce towards the earth. Maps of the moon (that is, the hemisphere which presents itself to us) are now as familiar to astronomers as maps of the world. The axis of the moon is almost perpendicular to the plane of the ecliptic. J. R.—The paragraph has been going the rounds of certain newspapers for some time, but it is incorrect. Five Sundays in February can only happen in some leap year. It happened in 1880, not “ last February.”