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POPULAR SCIENCE REVIEW. 
MARS. 
BY JAMES BREEN ; F.R.A.S. 
O P all tlie planets of the system; Mars, which for the last 
few months has been shining so brightly in the heavens, 
is that whose topographical details are best known to us. By 
glancing over the accompanying pictures of its telescopic aspect, 
we immediately perceive how much is revealed of its surface, — 
of its islands, continents, seas, and snows, by means of powerful 
optical aid. It is the planet which most strongly resembles the 
Earth in the duration of its days and seasons ; the existence of an 
atmosphere is everywhere apparent: being proved by the dimness 
of the dark streaks and spots at the circumference, as compared 
with their distinctness at the centre of the planet (for at the 
former the solar light has to penetrate through a dense stratum 
of air, and is again refracted through the same thick medium) ; — 
by occasional clouds passing over its sm-face ; — by the snow- 
zones piled up and stretching over vast spaces at its poles in 
the winter, which melt away gradually as the Sun ascends above 
the horizon in the summer, and dissipates the frost and darkness 
which for months previously had reigned in those arctic and 
antarctic regions. In the planet Jupiter a small telescope 
may more readily show the dark belts and spots ; but those are 
ever changing and drifting about with variable velocity; the 
terra firma is scarcely perceived on this immense body, which 
appears to have an economy of its own, hidden from us by 
great masses of cloud, through an occasional break of which we 
perhaps sometimes catch a glimpse of the dark body of the 
planet. On the surface of Mars, on the contrary, the dark 
spots preserve the same position and relative dimensions, and 
we appear to be looking at a miniature globe pencilled over 
with dim seas and continents. From year to year the sea does 
not appear to encroach upon the land, nor the land upon the 
ocean ; all the changes which are perceived are purely meteo- 
rological — the presence of clouds and murky weather, and snow 
during the winter, — of a clear atmosphere and sunny clime 
throughout the summer. 
The first circumstance we detect in looking at the planet 
Mars, is its exceedingly red light, which is quite different from 
