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 glorious nebulosity of Orion. The theory of probabilities allows reasonable beings to draw no other conclusion.

The theory of probabilities is also very instructive in the information which it gives us with reference to the existence of an invisible myriad of bodies through space which can never be discerned by any means at our disposal. It is, of course, well known that the stars, properly so-called, are each of them brilliant suns, intrinsically of majestic proportions, but dwarfed to comparative insignificance by the tremendous distance in space at which they are placed. These bodies are all self-luminous, and it may no doubt happen that there are dark bodies in the vicinity of some of the bright stars to which these stars act as illuminants, just in the same way as the sun dispenses light to the planets. But it is utterly impossible for us to discern objects illuminated in this fashion, for the light which they receive from suns that lie in their neighbourhood would be altogether insufficient to render them visible to us across the vast abyss of space by which they are separated from the earth. There are, no doubt, certain indirect processes of reasoning by which astronomers have learned, with more or less accuracy, something with regard to these dark stars. Thus, for instance, it has been shown that the extraordinary fluctuations in the light of Algol must be attributed to the eclipses of a brilliant star by the interposition at regular intervals of a dark body revolving around it. There are also cases in which it has happened that two dark stars have come so near each other that they may be almost said to have collided, and the sudden transformation of energy of motion into energy of light and heat has been sufficient to announce far and wide through the universe the character of the event which has taken place.