The first and most conspicuous of its characteristics is cloudlessness. A cloud is an event on Mars, a rare and unusual phenomenon, which should make it more fittingly appreciated there than Ruskin lamented was the case on Earth, for it is almost perpetually fine weather on our neighbor in space. From the day’s beginning to its close, and from one end of the year to the other, nothing appears to veil the greater part of the planet’s surface.
This would seem to be even more completely the case than has hitherto been supposed. We read sometimes in astronomical books and articles picturesque accounts of clouds and mists gathering over certain regions of the disk, hiding the coast-lines and continents from view, and then, some hours later, clearing off again. Very possibly this takes place, but not with the certainty imputed to it. It is also doubtful if certain effects of longer duration are really attributable to such cause. For closer study reveals another cause at work, as we shall see later, and the better our own air the more the Martian skies seem to clear. Certainly no instance of the blotting out of detail upon the surface of Mars has been seen this year at Flagstaff. Though the planet’s face has been scanned there almost every night, from the last day of May to time end of November, not a single case of undoubted obscuration of any