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 ECLIPSE 631 scope showed the green line (coronium) and D3 (helium) Africa were baffled by cloudy weather. Father Perry in the coronal spectrum. observed at Salute Islands, French Guiana, and obtained The eclipse of May 6, 1883, was observed from a small some photographs of value. The effort cost him his life, coral atoll in the South Pacific Ocean by parties from for he died of malarial fever five days after the eclipse. America, England, France, Austria, and Italy. A thorough The eclipse of April 16, 1893, was observed by British search was made by Holden (with a six-inch telescope) and French parties in Africa and Brazil, and by Professor for an intra-Mercurial planet, without success, during an Schalberle of the Lick Observatory in Chile. The Chile unusually long totality (5 m. 23 s.). Palisa also searched photographs of the corona were taken with a lens of 40 for such a planet. Janssen again reported the presence of feet focus, and are extremely fine. They show a faint dark lines in the coronal spectrum. “ White ” prominences comet near the sun. No great extensions to the corona were seen by Tacchini. were shown on any of the negatives, or seen visually, The eclipse of August 29, 1886, was observed in the though they were specially looked for by British parties. West Indies. The English photographs of the corona, The neighbourhood of the sun was carefully examined by taken with a slitless spectroscope, show the hydrogen lines Bigourdan without finding any planet. The spectrum of as well as K and/. Tacchini devoted his attention to the the corona was the usual one. The following lines were spectra of the prominences, and showed that their upper por- photographed in slitless spectroscopes, and undoubtedly tions contained no hydrogen lines, but only the H and K belong to the corona :—W. L. 3987 ; 4086 ; 4217 ; 4231; lines of calcium. He also observed a very extensive 4240; 4280; 4486; 5303 (the last number is the wave“white” prominence. It was shown on the photographs length of the green coronium line). All of these have of the corona, but could not be seen in the Ha line with been seen in slit spectroscopes also. It is possible that the spectroscope. It has been suggested by Professor two lines observed by Young in 1869, namely, W. L. (AngG. E. Hale that the colour of a “ white ” prominence may strom) 5450 and 5570, should be added to the list of unbe due to the fact that the H and K lines (calcium) are of doubted coronal lines. It is not likely that helium or their normal intensity, while the less refrangible prominence hydrogen or calcium vapour forms part of the corona. lines are, from some unknown cause, comparatively faint. The wave-lengths of some 700 lines belonging to the It is known that the intensity of such lines does, in fact, chromosphere and prominences were determined by the vary, though it is not yet certain that the “ white ” pro- British parties. minences are produced in this way. The subject is one The eclipse of August 9, 1896, was total in Norway and demanding further observation. High prominences are Nova Zembla. The day was very unfavourable, but good generally “ white ” at their summits, “ red ” at their bases. photographs of the corona were obtained by Russian The Harvard College Observatory photographs show the parties in Siberia and Lapland. Mr Shackelton, in Nova corona out to 90' from the moon’s limb, though no detail Zembla, with a prismatic camera obtained a photograph of is visible beyond 60'. Mr W. H. Pickering made a series the reversing-layer at the beginning of totality. This of photographic photometric measures of the corona, some photograph completely confirms Young’s discovery, and of which are given below, together with results deduced by shows the prominent Fraunhofer lines bright, the bright Holden from the eclipses of January and December 1889 :— lines of the chromosphere spectrum being- especially conspicuous. At the solar eclipse of January 22, 1898, the shadow of August January December 1886. 1889. 1889. the moon traversed India from the western coast to the Himalaya. The duration of totality was about 2 m. The eclipse was very fully observed, more than 100 negaIntrinsic actinic brilliancy of the brightest parts of the corona 0-031 tives of the corona being secured. The equatorial exten0-079 0-029 Do. of the polar rays. 0-053 0-016 sion of the visible corona was short and faint, and the Do. of the sky near the sun o-obor 0-0050 0-0009 invisible (spectroscopic) corona was also very faint. The Ratio of intrinsic brilliancy of the spectrum of the reversing-layer was successfully photobrightest parts of the corona to that of the sky (actinic) 44 to 1 16 to 1 32 to 1 graphed ; one set of negatives shows the polarization of one Magnitude of the faintest star of the longest streamers of the corona, and proves the shown on the eclipse negatives. 2-3 presence of dust particles reflecting solar light. The brightline spectrum of hydrogen in the chromosphere was followed The results in the first and third columns are derived from plates to the thirtieth point of the series, and the wave-lengths taken in a very humid climate, and are not very different. were shown to agree closely with Balmer’s formula (see The eclipse of August 19, 1887, was total in Japan and Spectroscope). The wave-length of coronium was found Russia, but cloudy weather prevented successful observa- to be 5303 (not 5317 as previously supposed), and the tions except in Siberia ^nd Eastern Russia. brightness of the corona was measured. Maunder made The eclipse of January 1, 1889, was observed in California the curious observation of coronal matter enveloping a proand Nevada by many American astronomers. The photo- minence in the form of a hood. graphs of the corona, especially those by Charoppin and Observations of the eclipse of May 28, 1900, were Barnard, show a wealth of detail. Those of Barnard, favoured in a remarkable degree by the absence of clouds. of the Lick Observatory party, were studied by Holden, The photographs of the corona obtained by Campbell and exhibited the fact that rays, like the “polar-rays,” extended four diameters of the sun on the west side. The extended all round the sun, instead of being confined to sun’s edge was photographed with an objective-prism the polar regions only. The outer corona was registered spectrograph composed of two 60° prisms in front of a out to 100' from the moon’s limb on Charoppin’s negatives, telescope of 2 in. aperture and 60 in. focus. A fine phototo 130' on those of Lowden and Ireland. On other plates graph, 6 inches long, of the bright- and dark-line spectra the outline of the moon is visible projected on the corona of the sun’s edge at the end of totality was thus obtained. before totality began. The spectrum of the corona showed It shows 600 bright lines sharply in focus besides the darkfew bright lines besides those of coronium and hydrogen. line spectrum, to which the bright lines gave way as the The eclipse of December 22, 1889, was observed in sun reappeared. The coronal material radiating the green Cayenne, S.A., by a party from the Lick Observatory light was found to be markedly heaped up in the sun-spot under rather unfavourable conditions. Expeditions sent to regions. No dark lines were found in the spectrum of the