This may explain the very rapid diminution of the polar ice-caps in the summer of either, but especially of the Southern hemisphere; and also the occasional appearance of large dark spots in their midst, where the shallow snow has probably been swept away by the rare storms of this planet from an extensive land surface.

It is supposed that no inconsiderable part of the ice and snow immediately surrounding the poles covers land; but, though balloon parties have of late occasionally reached the poles, they have never ventured to remain there long enough to disembark and ascertain the fact.
Towards evening the stream turned more decidedly to the north, and at this point Esmo brought out an instrument constructed somewhat on the principle of a sextant or quadrant, but without the mirror, by which we were enabled to take reliable measures of the angles.

By a process which at that time I did not accurately follow, and which I had not subsequently the means of verifying, the distance as well as the angle subtended by the height was obtained.

Kevima, after working out his father's figures, informed me that the highest peak in view--the highest in Mars--was not less than 44,000 feet.

No Martial balloonist, much less any Martial mountain-climber, has ever, save once, reached a greater height than 16,000 feet--the air at the sea-level being scarcely more dense than ours at 10,000 feet.