In referring to Saturn generally, we speak of its ring in the singular number, but, in point of fact, there are several rings—three in particular. The principal bright ring is really double, and within the innermost bright ring there is a dusky one, perfect as a ring, but not luminous as the outer rings are. By way of distinguishing one ring from another, it is usual to adopt Struve’s nomenclature, whereby the outermost bright ring is called A, the inner bright ring B, and the dusky ring C. A good engraving will convey more fully and more clearly an idea of what the Saturnian system consists of than the fullest verbal description will do. (See _Frontispiece_.) To the earliest astronomers who possessed telescopes, Saturn proved a great puzzle, because it seemed to undergo changes of shape which were quite inexplicable on any principles then known. Galileo, when first he saw it, thought it presented an oval outline which might be due to a central planet having a smaller planet on each side of it, and accordingly he announced to his friend, Kepler, that the most distant planet was _tergeminum_ or tri-form. But greater magnifying power led him to arrive at the conclusion that the planet was not a triple combination of spheres, but one body, either oblong or oval in outline. This conclusion, however, was soon found to be untenable, because the two (supposed) tributary bodies gradually decreased in size until they entirely disappeared. Galileo writing to his friend, Welser, in December 1612, thus expressed himself:— “What is to be said concerning so strange a metamorphosis? Are the two lesser stars consumed after the manner of the solar spots? Have they vanished or suddenly fled? Has Saturn, perhaps, devoured his own children? Or were the appearances indeed illusion or fraud, with which the glasses have so long deceived me, as well as many others to whom I have shewn them? Now, perhaps, is the time come to revive the well-nigh withered hopes of those who, guided by more profound contemplations, have discovered the fallacy of the new observations, and demonstrated the utter impossibility of their existence. I do not know what to say in a case so surprising, so unlooked for, and so novel. The shortness of the time, the unexpected nature of the event, the weakness of my understanding, and the fear of being mistaken have greatly confounded me.” [Illustration: Fig. 16.—General view of the Phases of Saturn’s Rings.]