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The photophone, although not strictly within the range of 

 subjects hitherto considered by our Society, is yet so intimately 

 connected mth the topics now under notice, that a passing refer- 

 ence must be made to this very wonderful invention. Mr. Graham 

 Bell has the honour of being the first to make known the remark- 

 able effects produced by this instrument. By its means sound is 

 conveyed, not by a string or wire, but by a beam of light. A 

 plain bright flexible mirror is fixed on a stand, the light thrown 

 upon it as a beam is reflected so as to strike a parabolic reflector 

 placed at a distance. In the focus of the parabolic reflector is 

 placed a cell of silenium connected with a galvanic battery and a 

 telephone. If a voice speak behind the flexible mirror vibrations 

 are produced, and these are communicated to the beam of light, 

 and the vibrations acting along the light produce a sound which 

 becomes audible by the telephone. It has been long known that 

 various metals and metalloids give sounds under the action of 

 light and heat; and, in addition to silenium, it is asserted that 

 gold, silver, platinum, iron, steel, brass, copper, zinc, lead, and 

 even paper, parchment, and mica are sensitive to light vibrations. 



Mr. Shelford Bidwell also succeeded in constructing a photo- 

 phone, differing in some respects from that of Mr. Graham Bell. 

 The transmitter is a thin disc of mici'oscopic glass silvered on its 

 anterior surface, and placed in front of a tube, by which the voice 

 is conveyed to it so as to excite vibration. The lime, or electric 

 light, is reflected fi'om this mirror through a con^-ex lens so as to 

 render the rays parallel ; these being received on a second lens at 

 some distance, and again concentrated on a silenium receiver. 

 The voice is conveyed across a space of ten feet into a neighbouring 

 room by this instrument. While experimenting with the photo- 

 phone the thought occurred to him that an instrument might be 

 constructed to transmit pictui'es of natural objects by means of 

 the electric current. Thus he would be able to telegraph not 

 merely symbols but actual portraits, and take a photo-picture 

 many miles from the object. He has so far succeeded as to show 

 that the problem is certainly not insoluble. A description of his 

 process, and of the instrument employed, is given in Nature, Feb. 

 10, 1881. Every one reading his account of his work must very 

 heartily wish that this pains-taking and accomplished physicist may 

 be successful in developing to perfection what he calls " Tele- 

 photography." 



