November 8th, 1927; May 10th, 1937; November 12th, 1940; May 13th, 1953, and November 6th, 1960.
The eccentricity of the orbit of Mercury is so pronounced that its greatest and least distance from the sun varies nearly 15,000,000 miles. This causes considerable variation in the speed of this planet, for as the sun does not lie in the center of the orbit but at one focus, it is not compelled to go as fast on the far side as on the side nearest to this tremendous mass. Being so close to the great attracting force of the sun, it is however, forced to move faster than any other planet in the solar system in order that the right balance of speed may be obtained to counteract the gravitational pull which would otherwise draw him instantly to the burning surface. Mercury's average rate of speed around its orbit is 35 miles a second. Neptune, seventy-five times as far off, feels so much less this relentless pull that it can roll leisurely along at the comfortable rate of 3.4 miles a second with no fear of being drawn to destruction.
Mercury completes his orbit in 88 days and this is, of course, the length of his year. During this journey he always turns the same face to the sun. The heat on this side must therefore be terrible and the surface unmercifully scorched and possibly cracked. Moreaux, a French astronomer, thinks that it may even be so hot that it has oceans of lead and molten tin. A few features are discernible, and although faint, these features are fixed. The general impression gained is that the tiny planet is barren, rough and mountainous, bleak, seared and desolate, with one side sweltering in terrific heat and the other numbed with dark and cold. Since there is no appreciable atmosphere on Mercury, there must be no wind—no warm currents of air to flow from the hot side to the cold side, nor from the cold side to the hot side,—thus making what is already drear seem motionless and dead.
Yet there is often some alleviating quality to make the drear
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