the conclusions that the greater part of Algol must be composed of matter in a gaseous state. Of course, such a state of things is already known to exist in many celestial bodies. The figures that have been arrived at must be regarded as subject to a possible correction, but it is difficult to repress all feelings of enthusiasm at a moment when, for the first time, so startling an extension has been given to our knowledge of the universe.
And now, as to the dark companion of Algol. Here is an object which we never have seen, and apparently never can expect to see, but yet we have been able not only to weigh it and to measure it, but also to determine its movements. It appears that the companion of Algol is about the same size as our sun, but has a mass only one-fourth as great. This indicates the existence of a globe of matter which must be largely in the gaseous state, but which, nevertheless, seems to be devoid of intrinsic luminosity. We may compare this body with the planet Saturn; of course, the latter is not nearly so large as the companion to Algol, but the two globes seem to agree fairly well as to density. As to the character of the movements of the dark companion of Algol, we can learn little, except what the laws of dynamics may teach; but the information thus acquired is founded on such well understood principles that it leaves us in no uncertainty.
It would be a natural assumption that the law of gravitation is obeyed and must be obeyed in the stellar systems. It would, indeed, be surprising if that law which regulates the movements of the bodies in the solar system should not be found to prevail in the sidereal systems also. Everything would justify us in the anticipation that this is so. Have we not learned to a large extent
