The spectroscope has taught us that the stars consist of incandescent solid bodies, or of masses of incandescent gas so large and dense as not to be transparent; and further, that they are surrounded by atmospheres consisting of gases cooler than themselves. The nature of the substances incandescent in the individual bodies has also to some extent been learned. The result has been to show that, while there is considerable variety in the chemical constitution and condition of the stars, at least five different types being recognised, each capable of more minute subdivision, the stars are, in the main, composed of elements similar to those existing in the sun; and, in Professor Newcomb's words, 'as the sun contains most of the elements found on the earth and few or no others, we may say that earth and stars seem to be all made out of like matter.' It is, of course, impossible to say what unknown elements may exist in the stars; but at least it is certain that many substances quite familiar to us, such as iron, magnesium, calcium, hydrogen, oxygen, and carbon, are present in their constitution. Indeed, our own sun, in spite of its overwhelming importance to ourselves is to be regarded, relatively to the stellar multitudes, as merely one star among many; nor, so far as can be judged, can it be considered by any means a star of the first class. There can be no doubt that, if removed to the average distance of first magnitude stars--thirty-three years light journey--our sun would be merely a common-place member of the heavenly host, far outshone by many of its fellow-suns. In all probability it would shine as about a fifth magnitude star, with suspicions of variability in its light. There remains to be noted the fact that the sun is not to be regarded as a fixed centre, its fixity being only relative to the members of its own system. With all its planets and comets it is sweeping continually through space with a velocity of more than 1,000,000 miles in the twenty-four hours. This remarkable fact was first suspected by Sir William Herschel, who also, with that insight which was characteristic of his wonderful genius, saw, and was able roughly to apply, the method which would either confirm or disprove the suspicion.