“A large number of trials of this apparatus have been made with the transmitting and receiving instruments so far apart that sounds could not be heard directly through the air. In a recent experiment Mr. Tainter operated the transmitting instrument, placed on the top of the Franklin School House in Washington, D. C.; the receiver being arranged in a window of my laboratory, at a distance of 213 metres. Upon placing the telephone to my ear, I heard distinctly from the illuminated receiver: ‘Mr. Bell, if you hear what I say, come to the window and wave your hat.’ “We have found that articulate speech can be reproduced by the oxyhydrogen light, and even by a beam from a kerosene lamp. The loudest effects follow upon interrupting the light by means of a perforated disk swiftly rotated. Because this apparatus is noiseless it allows a close approach of the receiver while not interfering with its message. “We have endeavored to ascertain the nature of the rays which affect selenium, placing in the path of an intermittent beam various absorbing substances. In these experiments Professor Cross has rendered us aid. When a solution of alum, or bisulphide of carbon, is employed, there is but slight reduction in loudness, but a solution of iodine in bisulphide of carbon cuts off most of the audible effect. Even an opaque sheet of hard rubber is less obstructive. [Illustration: A perforated disc rotated yields a succession of sounds from light.] 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