of Colour and Visible Motion. 121 



illustrated in the diagrams, or any others of the millions of 

 different and more complicated forms producible. Some may 

 change all their dimensions gradually in a certain direction, 

 while dimensions in the other directions remain unchanged; 

 others may alter all their dimensions in different directions 

 simultaneously, but with different velocities. Now, as we gaze 

 at the body with all these graceful complex motions, which can 

 readily be varied in shape or size of path, or in velocity of 

 description, the same sort of awe comes over us as must have 

 been felt by the people when they first listened to the strains of 

 the earliest musical instrument. 



To be sure it can never be as easy to change from a grave 

 circular swing to a quick and complicated motion as it is to put 

 down the key of a pianoforte ; and it may be long before me- 

 chanicians will be able to let us vary the motion with sufficient 

 rapidity. But we found that we could, even with our imper- 

 fect instrument, change one form of motion to almost any 

 other possible one in about a second ; and this is sufficiently 

 quick for the present educational state of the art. 



Our instrument itself we unfortunately cannot show, as it 

 is the property of the Japanese Government, and is in Japan. 

 Some photographs, however, of it and of our assistants who 

 took part in its construction and performances are lying on 

 the table. The exhibitions have been confined to ourselves 

 and our students ; but it was our intention, after we had edu- 

 cated ourselves by practising with the machine, to exhibit it 

 publicly. Unfortunately, however, from various delays con- 

 nected with improvements and alterations necessarily con- 

 nected with the designing of such a new machine, it was 

 hardly completed before one of the present writers left Japan, 

 and the other has now no opportunities to practise with it. 

 But it is our intention to construct a new instrument with 

 many improvements on the first model, one of the most im- 

 portant being the carrying out of the idea we had at the com- 

 mencement, of enabling the operator, by touching keys, to 

 give any desired brilliant or sombre coloration to the wall 

 on which the shadow of the body is moving, or to play on the 

 wall a changing mosaic. 



We will now describe the simplest form of our instrument, 

 represented in fig. 1 (Plate YI.j about one sixteenth of its 

 full size. 



B C is a roller which is turned by a handle D (not visible in 

 the figure), the fly-wheel E being of use in steadying the 

 motion. The roller is divided into three portions, B F, F G, 

 G C, by the circular collars at F and G ; at H, J, K, the 

 centres of these portions, the section of the roller is circular, 



