The eccentricity of the orbit of Mars is the cause also of his great variations in distance from us, and hence of his extreme changes in brilliancy. These changes are many times greater with reference to the earth than to the sun. At the planet’s nearest approach to us it comes a little nearer than thirty-five millions of miles. This is when it is in opposition in August. When opposition occurs in February, it is as much as sixty-two millions of miles from us; and when it is in conjunction, and on the other side of the sun from us, it is sometimes two hundred and forty-eight million miles distant. At his nearest approach light leaps over to us from Mars in about four minutes and eighteen seconds; at his greatest distance it cannot reach us in less than twenty-two minutes. The apparent mean diameter of Mars is about nine and fifty-six hundredths seconds, but varies from three and six-tenths seconds, when the planet is farthest away, to twenty-five seconds when it is nearest to us. While Mars does not exhibit the phases of the inner planets Venus and Mercury, by showing a disc sometimes at half-full and sometimes at crescent it is sufficiently near us to be, in certain positions, gibbous, or to show a little less than a full face. When this occurs Mars is about half-way between opposition and conjunction, and the earth and the sun are so situated that we are slightly to one side of the fully illuminated face of Mars. This phase, however, is not sufficiently marked to make any material difference in the brilliancy of the planet. It is not apparent without the aid of a telescope. From Mars the earth shows all the phases that Venus shows to us. When Mars is flaming down upon us in his position of greatest brilliancy we present to him a thin crescent. When he sees our full face we are on the opposite side of the sun from him. It would be necessary to have a more brilliant electrical illumination than any we have yet seen to lighten the dark side of the earth and exchange signals with Mars when we are nearest to him--if, indeed, our atmosphere would permit from Mars any view at all of the surface of the earth, which is not at all certain. In spite of its phases, the earth must shine on Mars at times in a very attractive way. It is not so bright, perhaps, as Venus is to us, nor as we are to Venus; but with our moon circling about us we may well be, when in a favorable situation, a very interesting double star, the distance between earth and moon appearing on Mars about equal to one-fourth of the apparent diameter of the moon. [Illustration: MARS: DIFFERENCE IN ITS APPARENT SIZE AT ITS NEAREST, MIDDLE, AND FARTHEST DISTANCE FROM THE EARTH Mars appears fifty times brighter when nearest than when farthest away.] DAY AND NIGHT, AND SEASONS