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Lettera al PROFESSOR LEWIS CAMPBELL. 26 febbraio 1874
   
 TO PROFESSOR LEWIS CAMPBELL.

   11 Scroope Terrace,
                                                               Cambridge, 26th February 1874.

     Jackson has sent me a MS. of yours about the mechanism of the heavens(14). After the interpretation of      , about which Greek appears to meet Greek as to whether it expresses motion or only configuration,   the main point seems to be, What is the motion and function of?

     (alpha) Is it in one piece with the sphere of the stars? or (beta) with that of the sun? or (gama) is it fixed in the   earth ?

     It is evidently a good stout axle, not a mere geometrical line, and it has some stiff work to do.

     What is this work?

     If the earth is fixed, and the great shaft has its bearings in a hole in the earth, then she (the earth) may, in virtue of   her dignity and office, cause the axle to revolve, carrying with it the stars according to alpha, or the sun according   to beta. Thus the earth may be the cause of the motion of the Same without moving herself, as a spinster is the   cause of the whirling of the spindle, though she does not herself pirouette.

     Or we may suppose the earth to act as one who twirls 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 sometimes 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. 

     I think I understand you to make Plato make the earth sit still and preside over the heavenly motions, and so   become the artifices of day and night, like a policeman who swings his bull's-eye round to his back. But his words   are capable of being used by the movers of the earth, as Milton says,

          If earth, industrious of herself, fetch day      Travelling east.

     I hope you will let me know whether I have not misunderstood both you, Plato, and the Truth. I have never   thanked you for your Œdipus, etc., which I have enjoyed. But at present I am all day at the Laboratory, which is    emerging from chaos, but is not yet cleared of gas-men, who are the laziest and most permanent of all the gods   who have been hatched under heaven(15).

Mrs. Maxwell joins me in kind regards to Mrs. Campbell and yourself.—Your afft. friend.