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HE facts with regard to the opposition of Mars in 1892 are sufficiently noteworthy to be stated with some detail, and we may first set them forth even at the risk of repeating a few things that will be familiar to those who have diligently studied the Nautical Almanack. It appears that the orbit of this particular planet is especially remarkable, among planetary orbits generally, for its departure from the circular form so nearly assumed in the movements of most of the other similar bodies. Mars has an orbit of so much eccentricity that its distance from the sun varies very considerably. It is sometimes as much as 153,000,000 miles off. It is sometimes as little as 127,000,000 miles. The orbit in which our earth revolves is much more nearly circular than is the orbit of Mars, but still the variations of the distance between the earth and the sun are too large to be overlooked, even though they may seem relatively unimportant. Under certain circumstances our earth may be as far from the sun as 93,500,000 miles, while the smallest magnitude to which the distance can shrink is 90,500,000 miles. These