the heavenly bodies. It is the application of the spectroscope by the labours of Sir W. Huggins and others that has disclosed to some extent the material elements present in the stars, as well as in comets and the distant nebulae. Now, however, it seems as if the spectroscope were for the future to be utilised not merely for that chemical examination of objects which is in the scope of no other method, but also as a means of advancing in a particular way our knowledge of the movements of the heavenly bodies. The results already obtained are of a striking and interesting description, and it is to their exposition and development that this article is devoted.
In the first place, it will be observed that the application of the spectroscope which we are now considering is not merely to be regarded as an improvement superseding the older methods of determining the movements of stars. It is, indeed, not a little remarkable that the type of information yielded by the spectroscope is wholly distinct from that which the earlier processes were adapted to give. The new method of observing movements, and that which, for convenience, we may speak of as the telescopic method, are not, in fact, competitive contrivances for obtaining the same results. They are rather to be regarded as complementary, each being just adapted to render the kind of information that the other is incompetent to afford.
It is well known that the ordinary expression, fixed star, is a misnomer, for almost every star which has been observed long enough is seen to be in motion. Indeed, it is not at all likely—nay, it is infinitely improbable, that such an object as a really fixed star actually exists. When the place of a star has been accurately determined
