The announcement was so startling that, as Miss Clerke says, “a clamour of contradiction was immediately raised, and a large amount of evidence on both sides of the question has since been collected.” Perrotin at Nice, Tacchini at Rome, Cerulli at Teramo, Mascari at Catania and Mount Etna, and Lowell in Arizona, all in favourable climates, confirmed Schiaparelli’s results, as also did a second series of observations by the Milan astronomer himself in 1895. On the other hand, Neisten, Trouvelot, _Camille_ _Flammarion_ (born 1842), and others, under less favourable climatic conditions, arrived at a period of 24 hours. _Aristarch Bélopolsky_ (born 1854), from spectroscopic observations at Pulkowa, by means of Doppler’s principle, found a period of 12 hours. Lowell, by the same principle, found, in 1901-03, a period of 225 days, in agreement with Schiaparelli’s results. This is the last word on the subject. Schiaparelli’s rotation period, confirmed by the theory of tidal friction, is generally accepted. That Venus has an atmosphere was one of the conclusions reached by Schröter in 1792; and in this at least he was correct, as the atmosphere of Venus, illuminated by the solar rays, has been seen extending round the entire disc of the planet. Spectroscopic observations by Tacchini, Ricco, and Young, during the transits of 1874 and 1882, indicated the existence of water-vapour in the planet’s atmosphere. Very little has been discovered regarding the “geography” of Venus. White patches at the supposed “poles” of the planet were observed in 1813 by _Franz von Gruithuisen_, and in 1878 by the French astronomer _Trouvelot_ (1827-1895). The secondary light of Venus, similar to the “old Moon in the new Moon’s arms,” was repeatedly observed since the time of Schröter by Vogel, Lohse, Zenger, and others. Vogel attributed it to twilight, and Lamp, a German observer, to electrical processes analogous to our auroræ. In 1887 a Belgian astronomer, _Paul Stroobant_, submitted to a searching examination all the supposed observations of a satellite of Venus, and was enabled to explain nearly all the supposed satellites as small stars which happened to lie near the planet’s path in the sky at the time of observation.