THE PLANETS. 



105 



The present form of things, and the exact numerical determ- 

 inations of their relations, has not hitherto been able to lead 

 us to a knowledge of the past states, or a clear insight into 

 the conditions under which they originated. These condi- 

 tions must not, however, on that account, be called accident- 

 al, as men call every thing whose genetic organ they are not 

 able to explain. 



3. Absolute and apparent Magnitude; Configuration. 

 — The diameter of the largest of all the planets (Jupiter) is 

 30 times as great as the diameter of the smallest of those 

 which have been determined with certainty (Mercury) ; near- 

 ly 11 times as great as the diameter of the Earth. Very 

 nearly the same relations obtain between Jupiter and the 

 Sun. Their diameters are nearly as 1 to 10. It has been 

 asserted, perhaps erroneously, that the distance of the me- 

 teoric stones, which there is a tendency to consider as small 

 planetary bodies, from Vesta, which, according to a measure- 

 ment- by Madler, is 66 geographical miles in diameter, there- 

 fore 80 miles less than the diameter of Pallas according to 

 Lament, is not greater than the distance of Vesta from the 

 Sun. According to these relations, there must be meteoric 

 stones of 517 feet in diameter. Fire-balls certainly have, 

 while they retain a disk-like appearance, a diameter amount- 

 ing to 2600 feet. 



The dependence of the flattening at the poles upon the ve- 

 locity of rotation appears most strikingly in the comparison 

 of the Earth as a planet of the interior group (Rot., 23''- 56'; 

 Flattening, ^^g) with the exterior planet Jupiter (Rot., Q*"- 55'', 

 Flattening, according to Arago, y^ ; according to John Her- 

 gchel, yV). and Saturn (Rot., 10^- 29'; Flattening, yV)- But 

 Mars, whose rotation is still 41 minutes slower than the ro- 

 tation of the Earth, has, even when a much smaller result is 

 assumed than that of William Herschel, very probably a much 

 greater flattening. Does the reason of this anomaly, inas- 

 .much as the figure of the surface of an elliptical spheroid 

 ought to correspond with the velocity of rotation, consist in 

 the difference of the law of the increasing density toward the 

 center of the superincumbent strata? or in the circumstance 

 that the liquid gurface of some planets was solidified before 

 they could assume the figure appertaining to their velocity 

 of rotation ? The important phenomena of the backward 

 motion of the equinoctial points or the apparent advance ot 

 the stars (precession), that of nutation (oscillation of the 

 Earth's axis), and the variation of the inclination of the 

 E 2 



