Solar and Planetary Evolation. 



61 



Xow, certain objections have been made to the nebular 

 theory, the most important of which is based upon the di- 

 rection of the rotation of the two outermost planets and their 

 satellites. The satellites of the inner series of planets, from 

 Mercury to Saturn, inclusive, revolve as the planets do, from 

 west to east. Those of Uranus, however, revolve nearly at 



Rotation 



of the 



outer 



planets, 



and 



retrofirade 



motion 



of tlie 



satellites. 



Rotation 



of the 



inner 



planets, 



and 



direct 



motion 



of the 



satellites. 



Fig. 6. ."Motion of planets and satellites if formed simultaneously, as by Faye's 



lij1)otliesis. 



right angles with the plane of rotation of the planet, Avhile 

 those of Neptune revolve in a reverse direction. This woukl 

 at first appear to be a serious objection to the tlieory ; but 

 recently the French astronomer, Faye, has i)ropounded an 

 hypothesis which explains this a})parent anomaly. (See 

 Figures 5 and G, above and on the opposite page.) Faye's 



