Experiments Without a Telephone.
“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 disturbance produced in crystalline selenium by the action of an intermittent beam of light should be audible in a similar manner with no telephone or battery. Many experiments were made to verify this theory; at first without definite results. The behavior of the hard rubber just mentioned suggested listening to it also. This was tried with an extraordinary result. I held the sheet in close contact with my ear while a beam of intermittent light was focussed upon it through a lens. A distinct musical note was immediately heard. Other substances, as enumerated at the outset of my address, were now successively tried in the form of thin disks, in every case with success. On the whole, we feel warranted in announcing as our conclusion that sounds can be produced by the action of a variable light from substances of all kinds in the form of thin diaphragms. The reason why thin diaphragms are more effective than masses appears to be that the molecular disturbance produced by light is chiefly a surface action, and that the vibration has to be transmitted through the mass of the substance in order to affect the ear. We have led air, directly in contact with an illuminated surface, to the ear by throwing the luminous beam upon the interior of a tube. We have thus heard from interrupted sunlight very perceptible musical tones through tubes of ordinary vulcanized rubber, of brass, and of wood. These were all the materials at hand in tubular form, and we have had no opportunity since of extending the observations to other substances. A musical tone can be heard by throwing the intermittent beam of light into the ear itself. This experiment was at first unsuccessful on account of the position in which the ear was held.”
CHAPTER XXVII
BESSEMER, CREATOR OF CHEAP STEEL. NOBEL, INVENTOR OF NEW EXPLOSIVES
Bessemer a man of golden ignorances . . . His boldness and versatility . . . The story of his steel process told by himself . . . Nobel’s heroic courage in failure and adversity . . . His triumph at last . . . Turns an accidental hint to great profit . . . Inventors to-day organized for attacks of new breadth and audacity.