Mars is the first planet whose orbit is exterior to that of the Earth, and when in opposition to the Sun, is a very conspicuous object, in the heavens, and of a fiery red colour; this, however, only takes place once in two years, the planet's synodic period being 780 days. When in perigee and in perihelion at the same time, as it is in opposition, Mars shines with a brilliancy rivalling Jupiter. Such was the case in August, 1719, when the planet was only 2½° from perihelion; its brightness was then so considerable as to give rise to a sort of panic. In order to be seen to the greatest advantage it must not only be in opposition, but also in perihelion at the same time; this occurs only once in 8 years.

Telescopically examined, Mars is found to be covered with numerous dusky patches; these are supposed to be the outlines of continents and seas analogous to those in our own globe: near the poles there are brilliant white spots, considered by many to be masses of snow; this idea is somewhat strengthened by the fact that they have been observed to diminish when brought under the Sun's influence at the commencement of the Martial summer; and increase again on the approach of winter.