406 THE CANADIAN NATURALIST. [Yol. ix. 



close approach of the receiver without interfering with the audi- 

 bility of the effect heard from the latter ; for it will be understood 

 that musical tones are emitted from the receiver when no sound 

 is made at the transmitter. A silent motion thus produces a 

 sound. In this way musical tones have been heard even from 

 the light of a candle. When distant effects are sought another 

 apparatus is used. By placing an opaque screen near the rotating 

 disk the beam can be entirely cut off by a slight motion of the 

 hand, and musical signals, like the dots and dashes of the Morse 

 telegraph code, can thus be produced at the distant receiving 

 station. 



We have made experiments, with the object of ascertaining the 

 nature of the rays that affect selenium. For this purpose we have 

 placed in the path of an intermittent beam various absorbing sub- 

 stances. Prof. Cross has been kind enough to give me his as" 

 sistance in conducting these experiments. When the solution of 

 alum, or bisulphide of carbon, is employed the loudness of the 

 sound produced by the intermittent beam is very slightly dimin- 

 ished ; but a solution of iodine in bisulphide of carbon cuts off 

 most but not all, of tlie audible effect. Even an apparently 

 opaque sheet of hard rubber does not entirely do this. When 

 the sheet of hard rubber was held near the disk interrupter the 

 rotation of the disk interrupted what was then an invisible beam 

 which passed over a space of about twelve feet before it reached 

 the lens which finally concentrated it upon the selenium cell. 

 A faint but perfectly perceptible musical tone was heard from the 

 telephone connected with the selenium. This could be interrupted 

 at will by placing the hand in the path of the invisible beam. 

 It would be premature, without further experiments, to speculate 

 too much concerning the nature of these invisible rays; but it is 

 difficult to believe that they can be bent rays, as the effect is pro- 

 duced throu2;h two sheets of hard rubber containing between them 

 a saturated solution of alum. Although effects are produced as 

 above shown by forms of radiant energy which are invisible, we 

 have named the apparatus for the production and reproduction of 

 sound in this way " J'/ie Photoplione,'^ because an ordinary beam 

 of light contains the rays which are operative. 



It is a well-known fact that the molecular disturbance produced 

 in a mass of iron by the magnetizing influence of an intermittent 

 electrical current can be observed as sound by placing the ear in 

 close contact with the iron. It occurred to us that the molecular 



