the two first mentioned, the right-hand one is the Gihon, the left-hand one the Hiddekel, and the spot at the limit of the latter is the Lacus Ismenius. From the pearl at the bottom of the Margaritifer Sinus, the Oxia Palus, the Oxus runs nearly north to the Pallas Lacus, while another canal, the Indus, makes off northwest.

Nearly in the centre of the disk are seen two of those strange comet-tail peninsulas that constitute so peculiar a feature of Martian geography. The lower is Deucalionis Regio; the upper, Pyrrhae Regio. Across them show two streaks, which, followed up, will be found to join other streaks traversing the dark regions. These introduce us to Mr. Douglass' discovery of a whole system of canals in the dark regions, paralleling the system in the bright areas,-- being similarly straight and similarly intersecting one another, with spots at the intersections, making what Mr. Douglass aptly terms a checkerboard effect, as we shall see more strikingly when we get round to the other side of the planet.

In Plate IV the markings have, under the rotation of the planet, all swung 30 degrees to the east, thus bringing others into view from the west. The great swath obliquely belting the disk is the canal called the Jamuna. It was, at the time this picture represents it, apparently in process of doubling. Crossing it obliquely is the Hydraotes. More conspicuous are two dark swaths that make with the Jamuna a nearly right-angled triangle. The lower one parallel to the edge of the disk is the Dardanus; the other, ending at the south with the Jamuna in the Aurorae Sinus, is the Ganges, one of the largest and most important of the Martian canals. At the date of the drawing, it was distinctly double. The doubling is very curiously prolonged by a narrow rectangle lying in the midst of the dark regions to the south. Some idea of the size of these strangely geometrical markings may be got by remembering that a degree on Mars represents thirty-seven miles. Skirting the edge of the dark regions westward, we come to a short canal, the Hebe, leading to the Fons Juventae, one of the tiniest markings perceptible on the disk, from which, however, some six canals have been found to radiate. Schiaparelli detected it in 1877, searched for it in vain in 1879, but at subsequent oppositions found it again, happier than Ponce de Leon in his futile quest after an earthly Fountain of Youth. Proceeding still farther west, we reach the entrance to the Agathodaemon, at the point where the edge of the dark regions abruptly trends southward. This canal brings us to the Solis Lacus region, one of the most interesting parts of the planet.

In Plate V. it has swung round into better view, where we will therefore consider it. The Solis Lacus is a great oval patch, measuring along its longest diameter five hundred and forty miles. With small telescopic power or in poor air it appears of uniform tint throughout, but under better visual conditions dark spots appear in it, and bright causeways, which divide it into five portions. Its longitudinal dividing line is prolonged into the Nectar, the short canal connecting it with the dark regions to the east. The Nectar thus appears double. Nor does the causeway stop here. It continues on between double dark lines until it reaches the long rectangular area spoken of before as a sort of continuation of the Ganges.

But a second feature of this region is no less noteworthy. Surrounding the Solis Lacus is a perfect cordon of canals and spots, the chief of which are the Tithonius Lacus, nearly due north, and the Lacus Phoenicis, or Phoenix Lake, northwest. The spots are strung like beads upon the loop of the Agathodaemon and the Daemon. From the northeast end of this string of spots runs the Chrysorrhoas to the Lacus Lunae on the fifty-eighth meridian. Below it is the Labeatis Lacus, from which the Gigas starts west, to be lost in the limb-light.

In the next plate (Plate VI.), the Solis Lacus is central, the Lacus Phoenicis somewhat to the right of the centre; and southwest of the Lacus Phoenicis is the Beak of the Sirens, the eastern end of the sea of the same name, which has just come round the corner of the disk. The canal connecting it with the Phoenix Lake is the Araxes; and at various angles to this, like spokes of a wheel about the Phoenix Lake for hub, are many more canals, the one lying most nearly due south being the Phasis. Connecting with this network of canals is a similar network of streaks in the dark regions, making a set of triangles, from which still other canals run up almost straight toward the south pole.