There remains only the theory that the Saturnian ring-system consists of discrete masses analogous to the streams of meteors known to exist in great numbers within the solar system. The masses may be solid or fluid, may be strewn in relatively vacant space, or may be surrounded by vaporous envelopes; but that they are discrete, each free to travel on its own course, seemed as completely demonstrated by Pierce's calculations as anything not actually admitting of direct observation could possibly be. The matter was placed beyond dispute by the independent analysis to which Clerk Maxwell subjected the mathematical problem. It had been selected in 1855 as the subject for the Adams Prize Essay at Cambridge, and Clerk Maxwell's essay, which obtained the prize, showed conclusively that only a system of many small bodies, each free to travel upon its course under the varying attractions to which it was subjected by Saturn itself, and by the Saturnian satellites, could possibly continue to girdle a planet as the rings of Saturn girdle him. It is clear that all the peculiarities hitherto observed in the Saturnian ring-system are explicable so soon as we regard that system as made up of multitudes of small bodies. Varieties of brightness simply indicate various degrees of condensation of these small satellites. Thus the outer ring had long been observed to be less bright than the inner. Of course it did not seem impossible that the outer ring might be made of different materials; yet there was something bizarre in the supposition that two rings forming the same system were thus different in substance. It would not have been at all noteworthy if different parts of the same ring differed in luminosity--in fact, it was much more remarkable that each zone of the system seemed uniformly bright all round. But that one zone should be of one tint, another of an entirely different tint, was a strange circumstance so long as the only available interpretation seemed to be that one zone was made (throughout) of one substance, the other of another. If this was strange when the difference between the inner and outer bright rings was alone considered, how much stranger did it seem when the multitudinous divisions in the rings were taken into account! Why should the ring-system, 30,000 miles in width, be thus divided into zones of different material? An arrangement so artificial is quite unlike all that is elsewhere seen among the subjects of the astronomer's researches. But when the rings are regarded as made up of multitudes of small bodies, we can quite readily understand how the nearly circular movements of all of these, at different rates, should result in the formation of rings of aggregation and rings of segregation, appearing at the earth's distance as bright rings and faint rings. The dark ring clearly corresponds in appearance with a ring of thinly scattered satellites. Indeed, it seems impossible