266 Dr. S. Toiver Preston on Certain Questions 



other view, would not be w T anting in interest (in respect to a 

 question so fundamental) , an excuse for quoting somewhat 

 at length from this letter may be deemed superfluous. The 

 experiment with the gyroscope (to be described) may be 

 noteworthy, less in relation to any actual novelty, than as to 

 possible practical conclusions derivable therefrom. Prof. 

 Pickering says : — 



" To my surprise I have found that the property of the 

 gyroscope which I am about to describe, although perfectly 

 elementary, appears to be little known either to physicists or 

 to astronomers. Neither is it mentioned in* the text-books, 

 as far as I am aware. That it has a very important bearing 

 on the mechanism of the solar system has been shewn in some 

 of my earlier papers. . . . 



" Suppose that while it [namely the gyroscope, mounted in 

 gimbals] is spinning, we set it upon a table, and cause the 

 stand supporting it to revolve slowly about its vertical axis. 

 Instantly the wheel will adjust itself so as to revolve in a 

 plane parallel to the surface of the table. 



" Furthermore, the direction of rotation of the wheel upon 

 its axis will be the same as the direction of rotation of the 

 stand. . . . 



" Another way of showing the experiment is to hold the 

 stand supporting the gyroscope at arm's length. The observer 

 then slowly revolves upon his heels, first in one direction and 

 then in the other. Each time the observer shifts his own 

 direction of motion the gyroscope will shift its plane, and 

 always in such a manner that its direction of rotation shall 

 be parallel, and in the same direction as its revolution in its 

 orbit. 



" It is a well-known fact that according to the nebular 

 hypothesis, all the planets should have rotated in a direction 

 opposite to that of their revolution in their orbits, just as 

 Neptune does at the present time. This is because by 

 Kepler's laws the inner edge of a revolving ring must neces- 

 sarily move faster than the outer edge. The fact that Neptune 

 is the only planet that even approximately fulfils this con- 

 dition has always been a source of trouble to the adherents 

 of the Nebular Hypothesis. No one has ever even attempted 

 to explain the anomalous rotation of Uranus, in a plane 

 practically perpendicular to the plane of its orbit. 



* Truly ;uiost text-books omit this subject, but a somewhat analogous 

 experiment may be found described in Prof. Perry's work ' Spinning 

 Tops,' p. 41. An elementary article on "The Mechanics of the Gyroscope," 

 by the present writer, which appeared in the journal ' Technics ' for July 

 1904 (George Newnes, Ltd.), may be alluded to incidentally here. 



