"Let there be light!" responded Gazen in a reverent manner, and instantly a soft, weird radiance was over all. The contrast of that sudden illumination with the preceding darkness was electrical in more senses than one, and I could not repress a cry of genuine admiration. A kind of twilight still reigned, and after the first moment of surprise, I perceived that we were standing on a light metal gangway in the middle of a great hollow cell of a luminous black or dark blue colour, relieved by innumerable bright points, and resembling the night sky in miniature. "I need hardly say that is a model of the celestial sphere," whispered Gazen, indicating the starry vault. "It is a wonderful imitation," I responded, my awestruck eyes wandering over the mysterious tracts of the Milky Way and the familiar constellations of the mimic heavens. "May I ask how it is done--how you produce that impression of infinite distance?" "By means of translucent shells illuminated from behind. The stars, of course, are electric lamps, and some of them, as you see, have a tinge of red or blue." Most of the light, however, came from a brilliant globe of a bluish lustre, which appeared to occupy the centre of the crystal sphere, and was surrounded by a number of smaller and fainter orbs that shone by its reflected rays. "This, again, is a model of the solar system," said Gazen. "The central luminary is, of course, the sun, and the others are the planets with their satellites." "They seem to float in air." "That is because their supports are invisible, or nearly so. Both their lights and periodic motions are produced by the electric current." "Surely they are not moving now?" "Oh, yes, and with velocities proportionate to those of the real bodies; but you know that whilst the actual movements of the sun and planets are so rapid, the dimensions of the system are so vast that if you could survey the whole from a standpoint in space, as we are supposed to do, it would appear at rest. Let us look at them a little closer." I followed Gazen along the gangway which encircled the orrery, and allowed us to survey each of the planets closer at hand. "This kind of place would make a good theatre for a class in astronomy," said I, "or for the meetings of the Interplanetary Congress of Astronomers, in the year 2000. You can turn on the stars and planets when you please. I wish you would give me a lecture on the subject now. My knowledge is a little the worse for wear, and a man ought to know something of the worlds around him--especially if he intends to visit them." "I should only bore you with an old story." "Not at all. You cannot be too simple and elementary. Regard me as a small boy in the stage of "'Twinkle, twinkle, little star, How I wonder what you are!'" "Very well, my little man, have you any idea how many stars you can see on a clear night?" "Billions."