concentric with the planet’s axis whilst the southern polar patch is eccentric to the extent of about 180 miles from the southern pole is one which has not yet received a satisfactory explanation. If both patches were eccentric so as to be exactly opposite to one another an explanation would be much more easy for we might say that the poles of rotation lay in one direction and the poles of cold in another. I have spoken on a previous page of three specially conspicuous shadings of Mars, and other similar shadings to the number perhaps of a couple of dozen were generally recognised by astronomers (having been mapped and named) down to about the year 1877. In that year the astronomical world was startled by the announcement that Schiaparelli of Milan, an able and competent observer, had discovered that those shaded areas which all previous astronomers had regarded as continents or vast tracts of land, were in reality islands, that is to say, so far, that the continents in question were cut up by innumerable channels intersecting one another at various angles. When this discovery was announced, and older observations and drawings came to be examined, it was found, or at any-rate thought, that these so-called canals might be traced in drawings of earlier dates by Dawes, Secchi, and Holden. So much for 1877. In December, 1881, the planet was again in opposition, but farther off in distance, and therefore smaller in size than in 1877. It was, however, higher up in the Heavens as seen at Milan and the weather appears to have been more favourable. In these altered circumstances Schiaparelli again saw his canals, but this time they were in at least as many as twenty instances seen in duplicate; that is to say, a twin canal was seen to run parallel to the original one at a distance of from 200 to 400 miles, as the case might be. The existence of not only single canals but of twin canals seems an established fact, for Schiaparelli’s drawings and descriptions have been confirmed by competent testimony; but explanation is nowhere; especially in view of Schiaparelli’s own idea that the duplication of his canals is perhaps not a permanent feature but a periodical phenomenon depending on, or connected in some way with, Mars’s seasons. [Illustration: Fig. 13.—Mars, August 27, 1892 (Guiot).]