But in 1877, during one of the highly favorable oppositions of that planet which occur but once in about sixteen years, the able Hall, using the great 26 inch refractor at Washington, discovered two tiny moons which had never been seen before.  One of these, called Deimos, is only six miles in diameter, the other, named Phobos, is only seven, and both are exceedingly close to the primary and in rapid revolution.  The diameter of these satellites is really less than the distance from High Park, on the west of Toronto, to Woodbine race course, on the east of the city.  No wonder these minute objects—­seldom, if ever, nearer to us than about forty millions of miles—­are difficult to see at all.  Newcomb and Holden tell us that they are invisible save at the sixteen year periods referred to, when it happens that the earth and Mars, in their respective orbits, approach each other more nearly than at any other time.  But once discovered, the rule held good even in the case of the satellites of Mars.  Pratt has seen Deimos, the outermost moon, with an eight and one-seventh inch telescope; Erek has seen it with a seven and one-third inch achromatic; Trouvellot, the innermost one, with a six and three-tenths glass, while Common believes that any one who can make out Enceladus, one of Saturn’s smallest moons, can see those of Mars by hiding the planet at or near the elongations, and that even our own moonlight does not prevent the observations being made.  It chances for the benefit of observers, in the northern hemisphere especially, that one of the sixteen year periods will culminate in 1893, when Mars will be most advantageously situated for close examination.  No doubt every one will avail himself of the opportunity, and may we not reasonably hope that scores of amateur observers throughout the United States and Canada will experience the delight of seeing and studying the tiny moons of our ruddy neighbor?

And so I might proceed until I had wearied you with illustrations showing what can be done with telescopes so small that they may fairly be classed as “common,” Webb says that such apertures, with somewhat high powers, will reveal stars down to the eleventh magnitude.  The interesting celestial objects more conspicuous than stars of that magnitude are sufficiently numerous to exhaust much more time than any amateur can give to observing.  Indeed, the lot of the amateur is a happy one.  With a good, though small, telescope, he may have for subjects of investigation the sun with his spots, his faculae, his prominences and spectra; the moon, a most superb object in nearly every optical instrument, with her mountains, valleys, seas, craters, cones, and ever-changing aspects renewed every month, her occupations of stars, her eclipses, and all that; the planets, some with phases, and other with markings, belts, rings, and moons with scores of occupations, eclipses and transits due to their easily observed rotation around their primaries; the nebulae, the double, triple and multiple stars with sometimes beautifully contrasted colors, and a thousand and one other means of amusing and instructing himself.  Nature has opened in the heavens as interesting a volume as she has opened on the earth, and with but little trouble any one may learn to read in it.