388 JAMES CLERK MAXWELL. [CHAP. XII. 



an expanded umbrella over his head about its stick as 

 an axis, the holes in the same representing the stars. The 

 objection to this view (which seems to me to be Jowett's) is 

 that in stating the relation between the earth and the axis, the 

 earth is said to be related to the axis (packed or whirling as 

 the case may be), and not the axis to the earth. Now, I 

 suppose that without all contradiction the less is related to 

 the better. Here the earth is like a ball of clay packed 

 round a graft on the branch of a tree, rather than like a field 

 in which, by means of a rotatory boring tool, men bore for 

 water. 



But the business of the earth is not so much to keep the 

 stars in motion as to effect the changes of night and day. 

 This she may do either by rotating herself from W. to E., 

 or by controlling the motion of the sun, by the help of the 

 great shaft. 



Now, if you always observe at the same time of night (a 

 common practice), ^you find the eastern stars higher every 

 day, and the western lower. All have the same motion, 

 which carries them round from E. to W. in a year. 



Mars, Jupiter, and Saturn, in spite of their wanderings 

 go on the whole in the same direction, but slower. Venus 

 and Mercury oscillate about the sun, and the moon goes the 

 opposite way from W. to E. 



That this way of viewing the matter was really prevalent 

 at one time is plain, from the expression the rising of such 

 a star to denote not a time of night but a time of year. It 

 means either (1) the day when the star rises, just before it is 

 lost in the brightness of the sun who follows it, or (2) the 

 day when the star is rising, when it just becomes visible 

 after sunset. 



Virgil, who speaks of stars rising, evidently had no 

 practical knowledge of what he meant. Plato, if he some- 

 times gets hazy, is far clearer than Virgil. Grote would 

 place him far below Mr. Jellinger Symons, who denied the 

 rotation of the moon, because Grote makes Plato say that 

 both the heavens and the earth rotate both in the same 

 direction, and with the same angular velocity. 



