Page:The Solar System - Six Lectures - Lowell.djvu/101

Saturn and its System

83

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With the hint given by this, at least singular, coincidence, let us examine the other satellite systems. Two others available for comparison present themselves, that of Jupiter and that of Uranus. Jupiter's system is this :—

No.	Name.				Diameter in Miles.					Distance from Jupiter in miles.
V.	(Nameless)	.	.	.	100	.	.	.	.	112,500
I.	Io	.	.	.	2,500	.	.	.	.	261,000
II.	Europa	.	.	.	2,100	.	.	.	.	415,000
III.	Ganymede	.	.	.	3,550	.	.	.	.	664,000
IV.	Callisto	.	.	.	2,960	.	.	.	.	1,167,000

Here, again, the largest body fills the centre of the field. With Uranus, we have:

No.	Name.				Diameter in Miles.						Distance from Uranus in Miles.
I.	Ariel	.	.	.	500	.	.	.	.	.	120,000
II.	Umbriel	.	.	.	400	.	.	.	.	.	167,000
III.	Titania	.	.	.	1,000	.	.	.	.	.	273,000
IV.	Oberon	.	.	.	800	.	.	.	.	.	365,000

The same relative agreement of position and mass !

Position of largest mass.Now consider the probability that this coincident arrangement should be due to chance. The greater mass might be found either at the beginning, in the middle, or at the end of the line. Take, as starting point, that it is found to occupy