Each of the maps presented marked in its day the point areography had reached; and each tells its own story better than any amount of text. They are all made upon Mercator’s projection and omit in consequence the circumpolar regions. The later ones give, too, only so much of the surface as was shown at the opposition they record, for Mars, being tipped now one way, now another, regards the earth differently according to its orbital position. In comparing them, therefore, the equator must be taken for medial line. Mercator’s projection has been the customary one for portraying Mars except for such oppositions as chiefly disclose the arctic pole. And this, too, with a certain poetic fitness. For it comes by right of priority to delineation of a new world; seeing that Mercator was the first to represent in a map the mundane new world in its entirety, by the rather important addition of North America to the southern continent already known, and to give the whole the title America with ‘Ame’ at the top of the map and ‘rica’ at the bottom. In looking at the maps it is to be remembered that they are what we should call upside down, south standing at the top and north at the bottom. Inverted they show because this is the way the telescopic observer always sees the planet. The disk would seem unnatural to astronomers were it duly righted. Just the same do men in the southern hemisphere look at our own Earth topsy-turvy according to our view, the Sun being to the north of them and the cold to the south. Certain landmarks distinguishable in all the maps may serve for specific introduction. The V-shaped marking on the equator pointing to the north is the Syrtis Major, the first marking ever made out upon the planet and drawn by the great Huyghens in 1659. The isolated oval patch in latitude 26° south is the Solis Lacus, the pupil of the eye of Mars; while the forked bay on the equator, discovered by Dawes, is the Sabaeus Sinus, the dividing tongue of which, the Fastigium Aryn, has been taken for the origin of longitudes on Mars. Twelve maps go to make the series. They are as follows:— MAKER DATE I. Map of Beer and Maedler 1840 II. Map of Kaiser 1864 III. Map of Flammarion (Résumé) 1876 IV. Map of Green 1877 V. Map of Schiaparelli 1877 VI. Map of Schiaparelli 1879 VII. Map of Schiaparelli 1881 VIII. Map of Schiaparelli 1884 IX. Map of Lowell 1894 X. Map of Lowell 1896 XI. Map of Lowell 1901 XII. Map of Lowell 1905