course, this may not be the case, and if it should prove to be unfounded, then some modification will have to be made in the numerical elements now provisionally assigned. There can, however, be little doubt that so far as the substantial features of the Algol system are concerned, the elements given by Vogel may be accepted.
Let us endeavour to form a conception of what Algol and its companion are like. It is worth making the attempt, because, as we have already said, Algol is the first star among "yonder hundred million spheres" of which the dimensions are approximately known. First we are to think of Algol itself. It is indeed a vast object, a glowing globe, a veritable sun, much larger than our own. The diameter of the sun would have to be increased by almost 200,000 miles to make it as great as that of Algol. But we may exhibit the relative proportions of the two bodies in a somewhat different manner. Imagine two globes, each as large as our sun; let those two be rolled into one, and we have a globe of the splendid proportions of Algol. But now for a singular circumstance which indicates the variety of types of sun which the heavens offer to our study, Though Algol is twice as big as the sun it is not twice as heavy. It is indeed an extraordinary circumstance that, notwithstanding the vast bulk of Algol, its weight is only about half that of the sun. The sun itself has a density about a fourth that of the earth, or but little more than the density of water, yet Algol has a density which is much less than that of water; in fact, this globe is apparently not much heavier than if it were made of cork. We are, of course, speaking of the average density of the star. No doubt its central portions must be dense enough, but it is impossible to resist
