252 



LETTERS ON NATURAL MAGIC. 



particles which compose that section at B, being at perfect 

 rest. By holding the rod at any intermediate point be- 

 tween A and B, so that the distance from A to the finger 

 and thumb is one-third, one-fourth, one-fifth, &c., of the 

 whole length A C, and rubbing one of the divisions in 

 the middle, the rod will divide itself into 3, 4, 5, &c., 

 vibrating portions, and give out corresponding harmonic 

 sounds. 



A rod of iron may be made to vibrate laterally or 

 transversely by fixing one end of it firmly as in a vice, 

 and leaving the other free, or by having both ends free or 

 both fixed. When a rod, fixed at one end and free at the 

 other, is made to vibrate, its mode of vibrating may bo 

 rendered evident to the eye ; and for the purpose of doing 

 this Mr. Wheatstone has contrived a curious instrument 

 called the KaleidopJione, which is shown in Fig. 43. It 



Fig. 43. 



consists of a circular base of wood A B, about nine inches 

 in diameter and one inch thick, and having four brass 

 sockets firmly fixed into it at C, D, E, and F. Into these 

 sockets are screwed four vertical steel rods, C, D, E, and 

 F, about 13 or 14 inches long, one being a square rod, 

 another a bent cylindrical one, and the other two cylin- 



