This body is the smaller of the two, and the speed with which it moves is double as great as that of Algol, so that it travels over as many miles in a second as an express train can get over in an hour. It revolves with apparent uniformity in an orbit which must be approximately circular, and it completes its journey in the brief period given above, which indicates the time of variability. So far the movements of Algol and its companion are not very dissimilar to movements in the solar system with which we are already familiar; but there is one point in which the Algol system presents features wholly without parallel in the planetary movements. It is that the two bodies are so very close together. I do not, of course, mean that they seem close by ordinary standards for is not their distance always some three million miles? This is, however, an unusually short distance when compared with the dimensions of the two globes themselves. The dimensions of the system may be appreciated by the simple illustration of taking a shilling and a sixpence and placing them so that the distance from rim to rim is two inches. The smaller coin will represent the dark satellite and the larger one Algol, fairly correct as to position and dimensions. Viewed in this way it is evident that the dimensions of the globes bear a monstrous proportion to their distance apart when compared with the more familiar planets and satellites of our system. The tides in such a case must be of a magnitude and importance of which we have no conception from our experiences of such agencies here.
We have dwelt thus long on the subject of Algol because it was fitting to give due emphasis to the remarkable extension of our knowledge of the universe
