The Transit of Venus: By George Forbes |
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accuracy accurately altazimuth altitude angle appears astronomer and photographer Astronomer Royal BALFOUR STEWART black drop British Expedition calculation chronometers coming transit cusps deduced determine the longitude different nations difficulty direction earth egress employed equatorial error GEORGE FORBES give Greenwich Halley Halley's method heliometer heliometric method Hence Horrox inferior planets ingress internal contact irradiation Jupiter Kerguelen's Island l'Isle's method large number least distance lens Lieut line of nodes Lord Lindsay Mars Mauritius measure Mercury method of durations micrometer miles minutes Monthly Notices moon motion observations of contact Observatory orbit of Venus Owens College pass phenomenon photo-heliograph photographic method plate Prof relay retarded round the sun Russians Sandwich Islands seen siderostat solar parallax star stations sun and Venus sun's centre sun's diameter sun's disc sun's distance sun's edge sun's parallax superior planets supposed telegraphic telescope tion transit of Mercury transit of Venus utilised Venus moves Yokohama
Popular passages
Page 99 - These Primers are extremely simple and attractive, and thoroughly answer their purpose of just leading the young beginner up to the threshold of the long avenues in the Palace of Nature which these titles suggest.
Page 77 - De l'Isle, originally fixed upon the following stations : — Alexandria, Sandwich Islands, Rodriguez, Kerguelen's Island, and New Zealand. No alteration has been made in the choice of these stations. Supplementary ones have, however, been added. Thus at Kerguelen's Island there will be two expeditions : one at Christmas Harbour in the north, and the other in the south of the island. In the Sandwich Islands there will be three stations : one at Honolulu, a second on the island of Hawaii, and a third...
Page 48 - ... of a milligramme, he might have a larger percentage error. When we consider how extremely small an angle the solar parallax is, it is astonishing to find so great a concordance between the results of different methods. As to the cause of the phenomenon of the " black drop," Lalande ascribed it to irradiation. Irradiation is that curious phenomenon in virtue of which a star, or any bright object, appears larger than it really is. If a thin platinum wire be intensely heated by the passage of an...
Page 99 - They are wonderfully clear and lucid in their instruction, simple in style, and admirable in plan. "—EDUCATIONAL TIMES. CHEMISTRY — By HE RoscoE, FRS, Professor of Chemistry in Owens College, Manchester. With numerous Illustrations. iSmo. is. New Edition. With Questions. "A very model of perspicacity and accuracy.
Page 52 - Transit of Venus made at Greenwich, the following facts appear : — 1. It requires considerable experience for an observer to appreciate all the definite changes of appearance which occur. 2. When two observers describe a particular phase which they see, and determine to observe this phase together, the times recorded by each are generally accordant within a fraction of a second. 3. The successive phases of an ingress or egress appear to follow each other sometimes rapidly, at other times gradually...
Page 99 - PHYSICS. LESSONS IN ELEMENTARY PHYSICS. By "BALFOUR STEWART, FRS, Professor of Natural Philosophy in Owens College, Manchester. With numerous Illustrations and Chromoliths of the Spectra of the Sun, Stars, and Nebulae.
Page 8 - In this apprehension I coincide with the opinion of the astrologers, because it is confirmed by experience ; but in other respects I cannot help despising their more than puerile vanities.
Page 54 - ... of measurement. There are two ways of applying the photographic method. The first is the same as the heliometric method. For this purpose it is necessary to have one station in the north and another in the south. By the other method we do not determine the least distance between the sun and planet, but the actual position of the planet at each observation. In other words, we determine the distance of Venus's centre from the sun's centre, and also the angular distance measured from the north point...
Page 54 - This is due to photogiaphic irradiation. It has been found by Lord Linds"ay and Mr. AC Ranyard to be mainly due to the reflection of light from the back of the glass plate.* It can be almost entirely avoided by wetting the back of the plate, and placing black paper against it. There will still be probably a slight enlargement of the sun's diameter. This will not affect the relative positions of the centres of the sun and Venus : but it will render it extremely difficult to determine the unit of measurement....