THE SMITHSONIAN INSTITUTION. 181 



directing attention to the revolving particles themselves, rather than 

 to the axes of motion, and as this mode renders more obvious the re- 

 semblance between comjtound rotary and compound redtVmear motions, 

 I will adopt that metliod of explanation in the remaining experiments. 

 The spherttid having lost considerable velocity, I renew it, and once 

 more direct the axis southward, observing that the particles on the west 

 side are moving doivnward. I now press the west side of the outer ring 

 towards the south, and you see that the only effect is to make the south 

 pole rise up ; if I push the same side iiorth, the south pole is depressed. 

 Now observe the reason. The particles on the west side, moving down 

 by one motion, and soiilh by the other, take an intermediate direction, 

 which necessarily elevates the south pole. The particles on the east 

 side conspire in this effect ; for, by the first rotation they move up- 

 ivard ; by the pressure which I communicate they are urged nor/A- 

 ward; and, taking a direction between these two, they 

 also throw the south pole itp. Thus every particle, 

 on the east half and on the west, has a compound 

 motion, which tends to raise the south pole of the 

 gpheroid ; that is^ to give the spheroid a revolution 

 on an axis between the two original ones, one of 

 which was directed horizontally southward, the other 

 vertically upward.* If the pressure is continued 

 gently for a few moments, the axis continues to rise, 

 always seeking a nev/ position, between its present 

 one and a vertical one, until, at length, it becomes vertical itself; then 

 the two revolutiuns coincide, and the ring for the first time yields to 

 the pressure, and goes round in the same direction as the spheroid. I 

 now give a new form to the experiment, by pressing the east side 

 southward for several seconds ; you perceive the north pole of the sphe- 

 roid elevating itself, till it finally points to the zenith, when the two 

 revolutions agree in a direction the reverse of the former. 



Another mode of exhibiting these last experiments is quite calcu- 

 lated to deceive the student and lead him to suppose that the diurnal 

 and annual revolutions of a planet or satellite, are performed in the 

 same general direction from some mechanical necessity. I whirl the 

 spheroid on a vertical axis, Irom west (through south) to east ; next 

 I confine the outer ring, by turning up the fork attached to the bot- 

 tom of the frame, so as to embrace the edge of the ring ; and then, 

 taking the frame by its two pillars, I commence carrying it round my- 

 self, from west to east. The spheroid, in the mean time, spins quietly 

 on its axis. But the moment I sto]) and begin to carry the frame 

 round from east to west, the spheroid suddenly throws itself over, and 

 revolves on a vertical axis still, but with its poles reversed. By this 

 inversion of axis, the spheroid revolves also from east to west, the 

 same direction in which I am carrying the frame. Once more I re- 

 verse the orbit motion, and instantly you see the spheroid turn over, 

 seeming determined (if I may borrow some convenient terms from 

 astronomy) to revolve diurnally in the same direction in which I carry 



. ^' Fig. 6. Tlie particles at A, moving by the revolution of the spheroid, and the pressure 

 of the rod, respectively in the directions of the In-okcn-shafl arrows, take the intermediate 

 direction indicated by the double-shaft arrow ; which can be done only by the rising of the 

 remote end of the axis. 



