These tints are seen when the skies are of their normal clearness, but after the occurrence of a great sand-storm in the desert and the upper air has become filled with fine sand particles, the Martian sunsets are equal in variety and depth of colour to anything seen on our earth during the months immediately succeeding the Krakatoa eruption. Those strange and intensely coloured sunsets will doubtless be remembered by my readers who had the good fortune to see them during the many months when they were visible after that great volcanic outburst in the year 1883.
Sand-storms have been unusually prevalent on Mars during the present summer, passing over large areas of country and obscuring the sun for considerable periods; so we have had several phenomenal sunsets afterwards.
As the time passed on the days became cooler--the evenings being considerably more so than on our earth in August, and twilight was very much shorter. Towards the end of the Martian August evening dews began to be succeeded by slight hoar frosts.
The heat in the tropics is not nearly so intense as on the earth. On the other hand, in the high latitudes near the poles, the summer temperature is higher than in similar latitudes on the earth, because upon Mars there is no permanent glaciation except right at the poles.
We have, of course, seen the Martian polar stars. The axial tilt of the planet being less than that of ours, and in a different direction, and its orbit being inclined 1° and 51' in regard to the earth's orbit, it follows that the poles of Mars must point to a different part of the sky, and a considerable distance from our polar stars.
In the northern hemisphere of Mars the polar star is a small one marked on our maps in the constellation of Cepheus, and it is almost on the boundary between that constellation and Cygnus. The pole star lies nearly in a line joining the brighter stars [alpha] Cephei and [alpha] Cygni.
The south polar star is a small one marked [symbol] in that part of the large constellation of Argo Navis which is termed Carnia.
Although the polar stars are very small, they shine more brightly in the Martian skies than the north polar star does to us, and are therefore more easily seen.