Page:History of the Royal Astronomical Society (1923).djvu/192

 164 HISTORY OF THE [1860-70 the Cape, and Williamstown, Victoria, resulted in a value of the solar parallax 8^-94 (Mem. R.A.S., 33, 77). Similar reductions made by Winnecke, of observations made in 1862 at Pulkova and the Cape, resulted in a parallax of 8" '-96. From a rediscussion of the observations of the Transit of Venus 1769, Stone, by a reasonable interpretation of some of the descriptions given by observers, deduced a solar parallax 8 "-91 (M.N., 28, 255). Thus it came about that Le Verrier's value of 8"95 was intro- duced in the Nautical Almanac for 1870, and continued in use until the Almanac for 1882, when Newcomb's value 8"-85 was adopted. Great preparations were made in 1868 for observing the total eclipse of the sun on August 17-18. Two expeditions were sent out from this country to India, one under Major J. T. Tennant, arranged by our Society, with the financial aid of the Indian and Imperial Governments : and the other under Lieut. John Herschel, R.E., arranged by the Royal Society, with financial aid from the Parliamentary grant annually placed at the disposal of that Society. This eclipse is made memorable by the success of the observa- tions which enabled both Tennant and Herschel to announce that the solar prominences exhibited bright lines in their spectra, indicating at any rate the presence of incandescent hydrogen and probably sodium and magnesium. Janssen's observations during the eclipse convinced him that he would be able to see the prominences with the help of his spectroscope in full sunlight, and he recounted how for two or three days after the eclipse he had been living in a veritable fairyland of new observations. Lockyer, working in London, with apparatus which had long before been designed for this particular research, but of which the com- pletion had been delayed for several months in a busy optician's workshop, was able to make announcement of the success of his observations. It arrived at the Paris Academy only a few minutes before Janssen's report from India, and the two investigators share the honour of the discovery of the new method. Another result of this eclipse was to bring about joint action between the Royal Society and our Society in making arrange- ments for the observations of the eclipse in 1870 December. This joint action was renewed from time to time, until in 1892 it ceased to be temporary by the appointment of a Joint Permanent Eclipse Committee of the two Societies. In reviewing the impressions gained in reading through the records available for this chapter in the history of the Society, one is led to feel that it was a decade of great and wholesome activity. The heritage of large problems from the previous decade