Looking up into the heavens we cannot fail to notice a broad, shining band that crosses the sky. We are early told that this is the Milky Way, receiving its name from its pale, silvery light and its path-like track across the firmament. All the heavenly bodies are arranged in clusters or nebulæ; no one of them is isolated. The Milky Way is one of these nebulæ. Its shape is that of a wide, irregular ribbon deeply notched at one end. The reason of the white and shining appearance of the entire nebula, is that it is densely crowded with stars, and is so immensely distant that the spaces between the stars are lost to view. About one hundred years ago Herschel endeavored to count the stars in the Milky Way. He found eighteen millions of stars in the central belt alone. How long is this nebula? Light starting from one limit of its longest diameter, and travelling one hundred and eighty-six thousand miles a second, would travel fifteen thousand years before it reached the last shining star in the Milky Way! Such distances as this are beyond our power to imagine. The Milky Way is a gigantic cluster of suns, and if each sun has its planetary system about it, each system rides like a shining archipelago in these seas of space. Earth and all other planets, being dark in themselves, do not count in these burning distances. So then our sun is but a star, and the Milky Way is made up of millions of such stars. More than this, our sun is one of the many stars that compose this wonderful band of light. We have now found our place in the heavens--we are a portion of the Milky Way. [Illustration: HUNG IN SPACE.] All the large stars which grace our most brilliant nights belong to this same great cluster. We are ourselves lying near its centre. Among all these suns our own appears to us to be the largest and most magnificent. This is because it is nearest to us, and it is to us the source of life, light, and heat. There may be other suns of tenfold splendor, and there may be other nebulæ far larger and more crowded with suns than the Milky Way. There are other nebulæ which have received different names, from the shape of their outlines, as globular, annular, spiral, double, multiple; the Crab, the ship Argo,--which is shaped like a comet,--the Magellanic clouds, and so on. These lie like splendid islands rocking in distant space, so far away, that if we travelled with the inconceivable speed of light, we might be millions of years in reaching them. Many of the greatest human minds have, during many ages, been occupied in studying our solar system, investigating its laws, measuring its distances. The discoveries so made have been applied to other systems, and in this way, by long and slow but sure degrees, the science of astronomy has been built up.