fact the range of slopes left in isolated insularity after all about it had melted away. From this we have an interesting bit of corroborative testimony that it stood on higher ground.

On August 11 the detached patch was yet farther separated from the main body of the cap, the smaller patch being many degrees distant to the north of either the geographical pole or the pole of cold, with water and even dry land to the south of it. It will be remembered, for the points of the compass, that this is the southern hemisphere of which we are speaking, and that, for climatic purposes, north and south here stand interchanged. On August 13 the detached patch is recorded for the last time, or, in other words, about this time it melted away. The larger one remained, contracting in size, however, as time went on. So it continued through August, September, and well into October.

On October 12, at 10h. 40m., I made the following entry about it: "Polar cap has been very faint for some time; barely visible." At 13h. 26m., or, in other words, at about half past one that night, Mr. Douglass measured its position and estimated its size, as was his wont every few days. He found it to be six degrees distant from the planet's pole, in longitude 54 degrees The patch was very small, covering about one hundred and fifty miles square. On looking at the planet on October 13, at 8h. 15m., to his surprise he found the cap gone. Not a trace of it could be seen; nor could either he or I detect it during the rest of that night although such was the longitude of the central meridian throughout it as to bring the cap on the nearer side of the pole, and therefore show it to best advantage. What had certainly been there on the 12th was not there on the 13th. The ice-cap had disappeared.

No such occurrence has ever been chronicled before. It is the first time since man began to observe the planet that the ice-cap has completely disappeared. Hitherto it has been seen to diminish to a minimum of from 7 to 4 degrees, and then begin to increase again. This last autumn, for the first time, it vanished entirely. The date of this occurrence was, in Martian chronology, about July 20. Evidently, for some reason unknown to us, it was a phenomenally hot season in the southern hemisphere of the planet.

Practically it never reappeared again during the season. That it did return occasionally, as a very small speck, was from time to time suspected, and doubtless did take place. Certainly it left for some time behind it a glimmer where it had been, due presumably to the moisture from its melting, still tarrying on the ground or lingering in the air. Otherwise, to all intents and purposes, where the polar ice-cap and polar sea had been was now one ochre stretch of desert.

Having thus followed to its vanishing point the polar cap, we will now return to it in the heyday of its youth, in June, 1894, when it was girdled by its broad blue belt. We have seen that we have reason to believe this to be in all probability a polar sea, a real body of water. There is, therefore, water on the surface of Mars. We also mark that this body of water is ephemeral. It exists while the ice-cap is melting, and then it somehow vanishes. What becomes of it, and whether there be other bodies of water on the planet, either permanent or temporary, we will now go on to inquire.

II. Areography

Areography is a true geography, as real as our own. Quite unlike the markings upon Jupiter or Saturn, where all we see is cloud, in the markings on Mars we gaze upon the actual surface features of the Martian globe. That we do so we know from the permanency of the spots and patches thus revealed to