MARS. 
233 
in addition, show the seas and continents of the planet to great 
advantage. In those three instances the snow-zones were 
touching the margins of the planets, hut in the second figure 
(taken by the writer on April 23, 1856, with the g-reat Cam- 
bridge Equatorial) the south, or uppermost pole, was quite iso- 
lated. As a proof of the brightness of the snow-spots, it may 
be mentioned, that on this occasion, when a cloud passed over 
and completely obliterated the planet, the snow-zones were 
quite large and bright, and appeared like faint stars struggling 
through the mist. 
Let us follow those spots through their regular changes. 
The planet comes into view on the Eai-th ; the northern part, 
after a winter season about as long as one of our years, again 
receives the beams of the Sun. The patch of snow, as it 
appears to us, at first large, diminishes gradually, and 
finally vanishes. After having had the companionship of the 
stars and of the night for a great interval, and passed a long- 
period under the dominion of darkness, the Sun appears, and 
to the protracted night succeeds the equally long day, with its 
fierce heat and fight. Nothing occurs between the fiery summer 
and the bleak and dark winter ; the other two seasons are 
wanting, but the one which is present amply makes amends 
for those which are absent, by the intense changes which take 
place in a comparatively short time. The Arctic seas, which 
were previously blocked up with solid ice or frozen snow, and 
have stopped the passage by sea and land, are gradually thaw- 
ing; the Northern again becomes liquid, the snows melt, the 
ice passes into its primeval condition, the land becomes passable, 
and the Sun — the cause of all this commotion — keeps in sight all 
day long, as if to tp-annize over those whom it has previously, 
by its absence, subjugated. The air becomes clearer, fogs have 
disappeared, the seas and continents have apparently a clear 
atmosphere overhead, — if we are to judge by the facility with 
which we view them, the November mists and murky atmo- 
spheres have been succeeded by a dry air and sunny skies. The 
opposite changes take place in the southern hemisphere, whilst 
these variations are progressing- in the northern. In the former, 
however, the extremes of heat and cold will be more severely felt. 
From the great eccentricity of Mars, the distance of the planet 
may vary betweenl31 andl58 millions of miles from the Sun ; but 
when it is summer in the southern hemisphere, the Sun is nearest 
the planet ; when winter, it is farthest from it. The quantity of 
heat and light received at those times by the southern portion 
of the planet are l-espectively 0-52 and O' 36 ; that of the Earth 
being- l’OO. The consequence is, that the summers are liotter 
and the winters colder on the southern than on the northern 
hemisphere. This is confirmed by observation ; for whilst the 
VOL. II. — NO. vi. R 
