ORIGINAL COMMUNICATIONS. 
The Rotation of CoLtourep Discs applied to facilitate the 
Study of the Laws of Harmonious Cotovurine, and to 
the MuutrexicatTion of Imaczs of Ossects into KaLEerpo- 
scopic ComBinations. By Joun Goruam, M.R.C.S., &e. 
In this paper I purpose to show how the rotation of 
coloured discs may be adapted—first, to assist in the inves- 
tigation of the laws of harmonious colouring, and secondly, 
to the construction of combinations of perfect symmetry of 
form and colour, which result from the multiplication of 
images of simple patterns used as objects. Such combina- 
tions are so beautiful that they may be said to vie with, even 
if not to surpass, those of the kaleidoscope; and although 
the principle of multiplication is different in the two instru- 
ments, yet the resemblance between the figures is sufficiently 
strong to induce me to designate the apparatus which pro- 
duces such forms by rotation as the Kaleidoscopic Colour- 
top. 
The possibility of forming an apparent mixture of two or 
more colours distributed on contiguous surfaces, by rotating 
them rapidly on a wheel, is founded on the well-known expe- 
riment of whirling a stick, ignited at one end, rapidly 
round in the hand, when a continuous circle of light is at 
once perceived, marking out the paths described by its burn- 
ing end. As the burning extremity can only be in one point 
of the path at the same instant, it is manifest that the im- 
pression of its light continues some time on the eye, and an 
uninterrupted circle of light is seen from the duration of 
successive impressions on the retina. Coloured surfaces, 
when revolved, form circular areas of colours in the same 
way, and if two or more differently coloured contiguous sur- 
faces are used, as many circular areas of different colours are 
formed, which being superposed produce the impression of 
mixture. It is obvious, therefore, that if a number of 
images of different colours occupy the field of vision simul- 
taneously, they will be perceived as one compound colour, 
just as when plates of differently coloured glass placed in 
apposition are viewed by transmitted light. The rotation ot 
colours may be considered, therefore, for practical purposes, 
as only another mode of mixing them. 
VOL. VII. G 
