In March and April of the year 1886 a study was made of the surface of Mars by W.F. Denning in England. Mr. Denning's drawings corroborated the charts of Green, Schiaparelli, Knobel, Terby and Baeddicker. He found the surface of Mars one of extreme complexity, a multitude of bright spots in places, but with a general fixity of character which led him to believe that the appearances were not atmospheric. He indeed attributed to Mars an attenuated atmosphere and thought that some of the vagaries in its surface characters were due to variations in our own atmosphere He did not find the Schiaparelli canals as distinct in outline as given by that ingenious observer. He noted many brilliant spots on Mars and indicated the disturbing influences of vibrations produced by winds on the surface of our earth in connection with changes in the earth's atmospheric envelope. In 1888 M. Perrotin continued his observations on the channels of Mars and noted changes. The triangular continent (Lydia of Schiaparelli) had disappeared, its reddish white tint indicating, or supposed to indicate, land, was then replaced by the black or blue color of the seas of Mars. New channels were observed, some of them in "direct continuation" with channels previously observed, amongst these an apparent channel through the polar ice cap. Some of these seemed double, running from near the equator to the neighborhood of the North Pole. The place called Lydia disappeared and reappeared. A strange puzzling statement was made that the canals could be traced straight across seas and continents in the line of the meridian. M. Terby confirmed many of these observations. Later the so-called "inundation of Lydia," observed by M. Perrotin, was doubted. Schiaparelli himself, Terby, Niesten at Brussels, and Holden at the Lick Observatory, failed to remark this change. These observers did not double the canals satisfactorily, but all agreed upon the striking whiteness and brightness of the planet. M. Fizeau (1888) argued that the Schiaparelli canals were really glacial phenomena, being ridges, crevasses, rectilinear fissures, etc., of continental masses of ice. Again (Bulletin de l'Academie Royale de Belgique, June) M. Nesten averred that the changes on the surface of Mars were periodic. In 1889, Prof. Schiaparelli reviewed what had been observed upon the surface of the planet in a continued article in _Himmel und Erde_, a popular astronomical journal published by the Gesellschaft Urania and edited by Dr. Meyer. Some remarkable photographs taken by Mr. Wilson in 1890 were commented on by Prof. W.H. Pickering in the "Sidereal Messenger." They showed the seasonal variations in the polar white blotches.