The wonderful music I heard upon Mars still rings in my ears; and, at times, so thrilling and peculiar is its effect upon me, that I feel as though I were being almost irresistibly impelled to return to that planet. Well, I should very much like to see the dear old Professor and Merna again, and also my many Martian friends. Then there's Siloni, whom I can never forget, for mentally her image is ever before me. What a nice girl she was! If I were to return to Mars, I wonder whether----? Printed by BALLANTYNE, HANSON & CO Edinburgh & London FOOTNOTES: [1] The exact diameters of the planets are difficult to measure owing to irradiation, and estimates of various authorities differ, especially with regard to the more distant planets. [2] Most probably the larger planets possess satellites which have yet to be discovered. [3] It is not yet ascertained with certainty whether Mercury and Venus rotate in about twenty-four hours, or whether the period is the same as that of their revolution round the sun. The evidence seems to point to the latter period. [4] The "terminator" is the boundary between the lighted and the dark portion of the disc. [5] Those who have seen the undercliff in the Isle of Wight will be able to form some idea of the terraces of the lunar ring-mountains, as they are very similar formations. [6] This is the case as regards separate satellites; but it may be pointed out that a similar thing must occur in regard to the rings of Saturn. The rings are composed of swarms of satellites so small that they can only be termed particles, and these particles at the inner edge of the "crape ring" revolve round Saturn in 5 hours and 33 minutes, the inner edge of the ring being only about 47,000 miles from the centre of the planet. The planet itself revolves on its axis in 10-1/4 hours. Thus, an immense number of these minute satellites must revolve round the planet in less time than it takes the planet to make one rotation. It is calculated that the particles in the outer edge of the next ring complete one revolution round the planet in 14 hours and 28 seconds. THE SCIENCE OF TO-DAY SERIES _With many Illustrations. Extra Crown 8vo. 5s. net._ AERIAL NAVIGATION OF TO-DAY. A Popular Account of the Evolution of Aeronautics. By CHARLES C. TURNER. "If ever the publication of a book was well timed, surely it is the case with this book on aviation.... Of the technical chapters we need only say that they are so simply written as to present no grave difficulties to the beginner who is equipped with an average education."--_Globe._ BOTANY OF TO-DAY. A Popular Account of the Evolution of Modern Botany. By Prof. G.F. SCOTT-ELLIOT, M.A., B.Sc., Author of "The Romance of Plant Life," _&c. &c._ "This most entertaining and instructive book. It is the fruit of wide reading and much patient industry."--_Globe._