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Page:Popular Science Monthly Volume 4.djvu/59

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THE RINGED PLANET.

by Saturnian action, its position is solely determined by Saturn's rotation, and it therefore remains constantly equatorial.

But next a very strange and, at a first view, incredible circumstance has to be considered in immediate connection with the relations we have been dealing with.

It sounds startling to suggest that Saturn probably changes at times in size and shape. Yet the evidence in favor of the suggestion is very weighty. It may briefly be presented as follows:

In April, 1805, Sir William Herschel, who had hitherto always seen the planet of an oval figure, found that it presented a strangely distorted appearance. It was flattened as usual at the poles, but also at the equator; accordingly, it had a quadrangular or oblong figure (with rounded corners, of course), its longest diameters being the two which (crossing each other in the middle of the disk) passed from north latitude 43° on Saturn to the same southerly latitude. Or we may otherwise describe the appearances presented, by saying that Saturn seemed swollen in both the temperate zones. Herschel found that the same appearance was presented, no matter what telescope he employed, and he tried many, some seven feet, some ten, one twenty, and one forty feet in length. With these telescopes Jupiter presented his ordinary oval aspect. But Herschel is not the only astronomer by whom such appearances have been noticed. On August 5, 1805, Schröter found that Saturn's figure was distorted. Dr. Kitchener says that in the autumn of 1818 he found Saturn to have the figure described by Herschel. The present Astronomer Royal has seen Saturn similarly distorted, and on another occasion flattened in the temperate zones. In January, 1855, Coolidge, with the splendid refractor of the Cambridge (U. S.) Observatory noticed a swollen appearance in Saturnian latitude 20°; yet on the 9th the planet had resumed its usual aspect. In the report of the Greenwich Observatory for 1860-'61, it is stated that "Saturn has sometimes appeared to exhibit the square-shouldered aspect." The two Bonds, of America, surpassed by few in observing skill, have seen Saturn square-shouldered and have noticed variations of shape. It seems impossible to reject such testimony as this. Nor can it be disposed of by showing that ordinarily Saturn presents a perfectly elliptical figure. It is the essential point of the circumstances we are considering, that they are unusual.

Now, we do not pretend to explain how such changes of shape are brought about. But we would invite special attention to the circumstance that if these changes be admitted as having occasionally occurred (and we do not see how they can be called in question), then the result is only startling in connection with that theory of Saturn's condition which we are here opposing. If Saturn be a globe resembling our earth, then sinkings and upheavals, such as these appearances indicate, must be regarded as involving amazing and most stupendous throes—as in fact absolutely incredible, no matter what evidence may