Mb. Hunt on the Cluephantic Colour Top. 255 



into that position produced a series of impressions, in each of which the 

 ball was in a different position, the whole combining to suggest the 

 rotation of the ball. In the top, however, the bright colour — yellow, 

 for example — in rotating very much faster than the perforated disc, 

 produces an impression through each circle in succession. The disc is, 

 however, moving round slowly, and by the time the yellow sector has 

 made a circuit, the disc has shifted to such an extent, as that the next 

 series of impressions is made in the positions of the first, through 

 different circles. The circles appear stationary, as the impressions are 

 repeated in the same positions ; but the balls appear to rotate, as in 

 each successive impression of any apparently stationary circle they 

 occupy a different position. 



The top with which the experiments were shown was a brass disc, 

 about five inches in diameter, with a brass spindle projecting down- 

 wards about an inch, and upwards about two and a-half inches. A nut 

 was screwed upon the spindle, to fix the coloured papers upon the top, 

 the top of this nut serving as a collar to support loose discs. It is, 

 however, better to provide a light frame, nicely fitted to the spindle, to 

 receive the loose discs. The retai'datiou may be effected by means of 

 vanes attached to this loose frame, and made capable of adjustment. 

 A simpler plan is to apply the finger as a friction brake to the rim of the 

 loose frame during the experiment. Mr. White, Optician, 1 Eenfield 

 Street, Glasgow, made the top shown, and can supply copies of it. The 

 top being spun by means of a string, the loose frame, with its disc,is dropt 

 on, and gradually acquires motion from the top. The ratio of the velo- 

 cities gradually changes through the experiment, and the effects change 

 also ; but in general one effect in each case comes out more brilliant 

 and satisfactory than any of the others ; when this is got, it may be 

 retained by a proper adjustment of the retardation. A very pleasing 

 experiment is made with a loose disc, with say four rings of apertures, 

 the outmost one having nine, the next eight, the next seven, and the 

 inmost one six apertures. The rings appear to rotate with different 

 velocities, and to be stationary in succession. An endless variety of 

 apparent motions may be obtained in this way — radial, circular, serpen- 

 tine, reciprocating, contrary, differential, &c., as will be easily under- 

 stood by those who have seen Mr. Rose's experiments. 



In some of the first experiments the coloiu's appeared softened, or 

 partially shaded into each other at their edges. The questions occurred, 

 whether this shading could be extended and improved, and if it could 

 be obtained without the multiplication of the colours. As with six 

 apertures five sets of the colours were shown, it was concluded that with 

 a smaller number of apertures, fewer sets would be got, but owing to a 



