12S COSMOS. 



Mercury 02056163 



Venus 0-0068618 



Earth 0-0167922 



Mars 0-0932166 



Jupiter. . 0-0481621 



Saturn 0-0561505 



Uranus 0-0466108 



Neptune 0-00871946 



The motion of the major axis (line of apsides) of the 

 planetary orbits, by which the place of the perihelion is 

 changed, is a motion which goes on perpetually in one di- 

 rection, and proportionally to the time. It is a change in 

 the position of the major axis, which requires more than a 

 hundred thousand years to complete its cycle, and is to be 

 distinguished as essentially different from those alterations 

 which the planetary orbits undergo in their form — their el- 

 lipticity. The question has been raised as to whether the 

 increasing value of this ellipticity is capable, during thou- 

 sands of years, of modifying, to any considerable extent, the 

 temperature of the Earth, in reference to the daily and an- 

 nual quantity and distribution of heat ? Whether a partial 

 solution of the great geological problem of the imbedding of 

 tropical vegetable and animal remains in the now cold zones 

 may not be found, in these astronomical causes, proceeding 

 regularly in accordance with eternal laws ? The same 

 mathematical arguments which excite apprehensions as to 

 the position of the apsides, the form of the elliptical planet- 

 ary orbits (according as these approach the circular form or 

 a cometary eccentricity), as to the inclination of the planet- 

 ary axes, changes in the obliquity of the ecliptic, the influ- 

 ence of precession upon the length of the year, also afford, 

 in their higher analytical development, cosmical grounds for 

 reassurance. The major axes and the masses are constant. 

 Periodic recurrence hinders the unlimited augmentation 

 of certain perturbations. In consequence of the mutual, and, 

 at the same time, compensating influence of Jupiter and Sat- 

 urn, the eccentricities of their orbits, in themselves slight, 

 are alternately in a state of increase and decrease, and are 

 also comprised within fixed, and, for the most part, narrow 

 amits. 



The point in which the Earth is nearest to the Sun falls in 

 very different periods of the year, in consequence of the al- 

 teration in the position of the major axis.^ If the perihelion 

 falls at the present time on the first day of January, and the 



* John Herschel, on the Astronomical Causes which may influence 

 Geological Phenomena, iu the Transact, of the Geolog. Soc. of London 

 2d 6erie£, vol. iii., pi. i., p. 298; the same in his Treatise on Astronomy 

 1833. {Cab. Cyclop., vol. xliii., $ 315.) 



