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minute bodies, perhaps little satellites, perhaps only particles like pebbles or dust, or perhaps like a cloud of smoke. This view had to be accepted, but was long without direct proof. The latter was finally brought out by Keeler with his spectroscope. He found that when the light of the rings was spread out into a spectrum, the dark spectral lines did not go straight across it, but were bent and broken in such a way as to show that the matter of the rings was revolving round the planet at unequal speeds. At the outer edge it revolved most slowly; the speed continually increased toward the inner edge, and was everywhere the same that a satellite would have if it revolved round the planet at that distance. This most beautiful discovery was made at the Allegheny Observatory near Pittsburg, Pa.

In making known his discovery of the satellite Titan, Huyghens congratulated himself that the solar system was now complete. There were now seven great bodies and seven small ones, the magic number of each. But within the next thirty years Cassini exploded all this mysticism by discovering four more satellites. Then, after the lapse of a century, the great Herschel found yet two more. Finally, the eighth was found by Bond at the Harvard Observatory in 1848.

In 1898 photographs of the sky taken at the South American branch of the Harvard Observatory showed a star near Saturn, but farther than the outermost known satellite, which seemed to be in a different position each