174 Nature's /iMraclcs. 



strength in the various wires will correspond 

 to the intensity of light reflected by the dif- 

 ferent sections of the picture. The shutters 

 are so adjusted that the amount of opening 

 depends upon the strength of current. The 

 shutters corresponding to the high lights of 

 the picture will open the widest and throw the 

 strongest light upon the screen, from a source 

 of light that is placed behind the shutters. 

 The shutters that open the least will be those 

 that are operated upon by the shadows of the 

 picture. Inasmuch as a picture thrown on a 

 screen from a source of light is wholly made 

 up of lights and shadows, the theory is that 

 this apparatus perfectly constructed would 

 transmit any picture to a distance, through 

 telegraph-wires. It must not be understood 

 that the rays of light are transmitted through 

 the wires as sound-vibrations are. Light, per 

 se y can be transmitted only through the lumi- 

 niferous ether, as we have seen in the chapter 

 on light in Volume II. 



While we are talking about these curious 

 methods of telegraphic transmission, I wish to 

 refer to an apparatus constructed by the writer 

 in 1874-5, for the purpose of receiving musical 

 tones or compositions transmitted from a dis- 

 tance through a wire by electricity. (A cut 

 of this apparatus is shown on page 875 of 

 " Electricity and Electric Telegraph," by 

 Prescott, issued in 1877.) It consists of a disk 



