92 



EECEEATIVE SCIENCE. 



one single revolution of tlie disc B. When 

 these relative velocities are maintained, five 

 groups of all the colours distributed on the 

 colour-disc are seen occurring in the order of 

 their arrangement on the disc, and repeated 

 in perfect symmetry in the various openings of 

 the patterns. In this way the most beautiful 

 variations may be effected by using different 

 colours in various proportions on the disc a ; 

 for, however numerous the colours, each 

 colour is reflected through its proper open- 

 ing in the disc B, at a given interval of space 

 and time, without the slightest irregularity 

 or confusion. Fig. 2 represents a non- 

 rotating disc, and Fig. 1 the same during 

 rotation. 



In order to retard the motion of the disc 

 B, and, at the same time, to produce the vibra- 

 tions, the central aperture is made sufficiently 

 large to admit of free motion on the spindle ; 

 and there is appended, at or near its circum- 

 ference, a light weight, such as a piece of 

 string or silk, which, by its impulses on the 

 atmosphere during rotation, both retards the 

 motion and produces the vibrations. The 

 proportion of the diameter of the central 

 aperture of the disc B to that of the spindle 

 of the colour-top is about as four to three— 

 an aperture of four-tenths of an inch, for 

 example, to a spindle three-tenths of an inch, 

 is very effective. 



As in the kaleidoscope, so in this instru- 

 ment, there is only one position for the situa- 

 tion of the eye with respect to the discs where 

 the symmetry of the combinations is perfect, 

 namely, vertically over the spindle of the top, 

 BO that the whole of the circular field can be 

 distinctly seen. 



For the purpose of giving variety to the 

 figures formed by the instrument, an assort- 

 ment of fantastic patterns on separate discs 

 may be constructed to take the place of the 

 disc B ; the disc a is also furnished with dif- 

 ferent colours. A disc of pure white forms 

 exquisite gray combinations, with every con- 

 ceivable variety of light and shade ; a disc of 



white and green, in equal portions, is resolved 

 into these elements, and their midtiplication 

 into a composite form is very agreeable to the 

 the eye. An elegant arrangement, whereby 

 patterns may be coloured in the most attrac- 

 tive manner, is composed of half a disc of 

 blue, and the rest of white, green, and red, in 

 equal proportions. 



To the artist this instrument will prove of 

 service in enabling him to select any number 

 of colours in any proportion, and to adjust 

 them instantaneously into a symmetrical 

 pattern. He will thus be enabled to ascer- 

 tain whether his selection of colours is har- 

 monious, and he will be able to put to the test 

 some of those beautiful harmonies which are 

 introduced into the more recent works on 

 colour. The following arrangement, adapted 

 from Sir J. Grardner Wilkinson's work on 

 Colour and Taste, will serve as an example : — 



On the disc a arrange, in the following 

 order and proportions, the colours : — Blue 

 129'' ; Scarlet, 42" ; Crimson, 37° ; Orange, 

 19° ; Yellow, 52° ; Green, 41° ; White, 4D\ 



Place such a disc on the colour-top, and 

 rotate ; during rotation drop down upon the 

 spindle any of the black perforated discs with 

 strings appended to them : the colours of the 

 disc A will now reappear multiplied, and pre- 

 senting themselves here and there, filling up 

 the open patterns of the perforated disc b, 

 and forming a polychrome ornament, the 

 beauty of which can scarcely be surpassed. 



The pictures thus presented to the eye 

 are very beautiful. Their charm would 

 appear to depend partly upon their being re- 

 flected to the eye through a perfectly black 

 medium, which imparts brilliancy and illumi- 

 nation to the colours, and partly upon their 

 being exhibited in a state of motion, the 

 apparent and real direction of which bear no 

 relation to one another. While the disc is 

 actually performing one hundred revolutions 

 per minute, and vibrating about thirty times 

 during each revolution, the combinations 

 themselves often appear hanging in space, 



