never, I believe, been distinctively noted or commented on before, which is singular, considering how conspicuous it was at Flagstaff. It is specially remarkable that it should never have been remarked upon elsewhere, in that a similar one girdling the north polar cap was seen by Beer and Mädler as far back as 1830. For it is, as we shall shortly see, a most significant phenomenon. In the first place, it was the darkest marking upon the disk, and was of a blue color. It was of different widths at different longitudes, and was especially pronounced in tint where it was widest, notably in two spots where it expanded into great bays, one in longitude 270° and one in longitude 330°. The former of these was very striking for its color, a deep blue, like some other-world grotto of Capri. The band was bounded on the north, that is, on the side toward the equator, by the bluish-green areas of the disk. It was contrasted with those both in tone and tint. It was both darker and more blue.
The band not only varied in width at different longitudes, but its width corresponded to the amount of the blue-green areas of the disk visible at these longitudes below it. It was widest where these were greatest in extent, and narrowest where they were least. If we consult the map of Mars we shall see that below the bay in longitude 330° lies the great dark
