The aim of the following pages is to illustrate, by the study of a few examples chosen almost at random, the variety in character of astronomical discoveries. An attempt has indeed been made to arrange the half-dozen examples, once selected, into a rough sequence according to the amount of "chance" associated with the discovery, though from this point of view Chapter IV. should come first; but I do not lay much stress upon it. There is undoubtedly an element of "luck" in most discoveries. "The biggest strokes are all luck," writes a brother astronomer who had done me the honour to glance at a few pages, "but a man must not drop his catches. Have you ever read Montaigne's essay 'Of Glory'? It is worth reading. Change war and glory to discovery and it is exactly the same theme. If you are looking for a motto you will find a score in it." Indeed even in cases such as those in Chapters V. and VI., where a discovery is made by turning over a heap of rubbish--declared such by experts and abandoned accordingly--we instinctively feel that the finding of something valuable was especially "fortunate." We should scarcely recommend such waste material as the best hunting ground for gems.