Mars and Its Mystery (Illustrated‪)‬

“Had some one asked, fifty years ago, Is the Sun composed of chemical elements with which we are familiar? Shall we ever know? the question would not have been deemed worthy of a second thought. Realizing what has been accomplished, not only regarding the constitution of the Sun, but of the most remote stars, we are encouraged to ask: Is Mars inhabited? Shall we ever know? To what groups of students are we to appeal for an answer? If we want to know the diameter of Mars, its weight, the form of its orbit, the inclination of its axis, the period of its revolution around the Sun, and its rotation period, its ephemeris and its albedo, we ask the astronomer, for he has the instruments with which to observe and measure, and the mathematical knowledge necessary to reduce the measurements.”