TRANSIT OF VENUS.

New Zealand Times, Volume XXIX, Issue 4277, 4 December 1874, Page 2

TRANSIT OF VENUS.

Sin,—By Hie kindness of Major Palmer, I have received a copy of his letter of instructions on the transit of Venus. The following digest of it, and a tew other particulars, may be acceptable to your readers : When Arenas, on her entrance upon the Sun, is nearly within the Sun her shape will alter. A black "drop ” will form from Venus to the Sun’s edge ; or, in a good telescope, Venus will look like a peg-top. (I.) AVatch tor a change of color in this drop ; (2.) watch very carefully for the instant when the drop breaks ; (3.) watch if there bo any haziness lingering behind, and the instant of its disappearance. (2.) is the most important point to be observed. Tile same appearances will be noted at the egress of the planet. (1.) Haziness; (2.) the formation of the drop ; (3.) change of color on the drop. Again, (2) is the important phenomenon. An observer should have a good chronometer, and should note the times of each appearance at once, and should make a drawing of what ho has seen as soon as possible. Tire chronometer's error, if any, and rate should bo ascertained both before and after the transit. If Venus crosses a Sun spot, any change in color should he noted. It would be well to take the times of crossing accurately. A haze has been noticed around Venus and Mercury in transit. A bright spot was seen by observers on Mercury when in transit. A watch must bo kept for anything of the sort. Venus may have a satellite, although most astronomers have given up the old records of its appearance, as in error. It would be well to watch for any dark spot moving across the Sun with Venus. If anything be seen an accurate drawing must be made of the size of the spot, and of its distance from A’cnus. The following plan gives the point of Venus’s first appearance Suppose the Sun's disc to bo figured as a clock face, then Venus will touch the Sun at sixteen minutes past the hour, and leave the Sun at twentyfour minutes past, entering at twenty-five minutes past one, on AVedncsday afternoon, December 9th, and leaving the Sun at nearly six o’clock. These places and dates are for ordinary telescopes, and for the naked eye. I shall be very glad to show the transit at the Observatory, between two o’clock and five o'clock. It is requested that, visitors will not come before two o’clock, and will all leave at five o’clock. It is most important that there should bo perfect quiet for the observers at the critical times of ingress and egress. I need hardly say that the prophecies credited to me about the bad weather, and the three days darkness at the transit, are no prophecies of mine. Therg will be, of course, no effect on the weather, and no alteration in the light of the Sun. If a piece of smoked glass be secured to the eyepiece of an ordinary telescope Venus will bo easily seen when upon the Sun. I hope to see it with the eye alone, using such a darkened glass.—l am, Ac., A. SI'OOK.