_Discovery of Satellites and of Canal-shaped markings._—The interest in this planet has been accentuated in recent years by several circumstances. The discovery of two satellites in 1877 by Prof. Hall, with the 25·8-inch Washington refractor, caused the directors of large instruments to test their capacity upon these minute objects. Schiaparelli’s observations of the canal-shaped markings have afforded another attractive feature in connection with this planet. He detected a network of dark straight lines stretching generally from N. to S. across the planet; and in the winter of 1881 found these objects duplicated, _i.e._ the lines ran in pairs so close together that they were separated with difficulty. The study of the topography of Mars had never previously revealed structures like these; yet the Italian astronomer appears to have observed them with “comparative ease whenever the air was still.” Other observers have not wholly confirmed the appearances alluded to, but no favourable opposition has occurred since 1877, and no surprise need be felt that the delicate features visible in the pellucid sky of Italy should elude detection in less genial climes. In 1886 M. Perrotin, at Nice, using a 15-inch equatoreal, saw a number of the “canals,” and some of them were double. In 1888 the observers having charge of the 36-inch refractor at Mount Hamilton re-observed the “canals” as broad bands, but none of them appeared to be duplicated. The conditions were unfavourable, the planet being more than three months past opposition.
Prof. Schiaparelli re-observed the duple “canals” in June 1890 with a refractor by Merz of 18 inches aperture, powers 350 and 500. His observations are supported by Mr. A. S. Williams, of Brighton, who informs me that he detected forty-three of the “canals,” and seven of them were “clearly and certainly seen to be double.” Mr. Williams’s instrument is a 6½-inch reflector by Calver, and powers of 320 and 430 were successfully employed on it; magnifiers under 300 were found of little use.
_Summary of Observations._—From observations at Bristol I have drawn up the following summary as to the configuration of Mars:—
1. That the “Hour-glass” or “Kaiser Sea,” and some other markings of analogous character, present very bold, dark, and clearly defined outlines, enabling them to be visible in very small telescopes. In 1873 I saw certain spots with a refractor of only 1-3/4-inch aperture. Mr. Grover, in 1867, “made a set of pencil-drawings, with a 2-inch telescope, which gave the general markings of the planet very well.” In ‘Recreative Science’ it is mentioned that on June 7, 1860, a semi-circular dark spot on the N.W. part of the disk of Mars was distinctly seen with a 1½-inch telescope, power 120.