PHYSICS. • 359 



Preoce has made some experiments on the conversion of sonorous 

 vibrations into radiant energy. The conchision to which he came was 

 that the disk itself did not vibrate at all, but that the effect is essen- 

 tially due to the expansion and contraction of the air contained in the 

 air space behind the disk, the sonorous effects being materially assisted 

 by coating the sides of the containing vessel with a highly absorbent 

 substance, such as the carbon deposited by burning camphor. {Proc. 

 Roy. Soc, March, 1881, xxxi, 50G; Mature, March, 1881, xxiii, 496.) 



In a second memoir, which was presented to the National Academy 

 of Sciences April 2 1, 1881, Graham Bell has given an account of the fur- 

 ther researches made by Tainter and himself on the production of sound 

 by radiant energy. While in Paris, in the fall of 1880, a new form of 

 the experiment occurred to Bell which would enable him to test the 

 question whether sonorousness under the influence of intermittent light 

 is not a property common to all matter. Preliminary experiments were 

 made, and were so promising that they were communicated to the French 

 Academy on the 11th of October. On the 2d of November he wrote to 

 Tainter, in Washington, as follows: "Place the substance to be experi- 

 mented with in a glass test-tube; connect a rubber tube with the mouth 

 of the test-tube, placing the other end of the pipe to the ear ; then focus 

 the intermittent beam on the substance in the tube." In January, on 

 returning to Washington, Bell found that Tainter had made the experi- 

 ments on a large number of substances, and had found that cotton- 

 wool, worsted, silk, and fibrous materials generally jiroduced much 

 louder sounds than hard, rigid bodies like crystals or than diaphragms. 

 Black worsted giving so good a result, he desired to try black cotton- 

 wool; but having none at hand he made some by mixing some lamp- 

 black with the cotton. The effect was so marked that he tried lamp- 

 black alone, with entire success. It was the loudest material yet used, 

 and was immediatelj" utilized in the construction of an articulating 

 photophone in place of the selenium receiver. The transmitter as well 

 as the receiver had a diaphragm 5 centimeters in diameter, and the 

 distance between the two was 40 meters. No heliostat or condensing 

 mirror was used; and words spoken into the transmitter in a low tone 

 of voice were readily audible in the lampblacked receiver. With refer- 

 ence to Preece's experiments. Bell maintains that the disks themselves 

 vibrate, as a loud sound is heard from a Blake transmitter when the 

 intermittent beam is focused on its disk. An ingenious experiment 

 devised by Tainter seemed to confirm this beyond dispute. Experiments 

 with liquids and with gases are recorded ; and two receivers where lamp- 

 black is used in place of selenium are described. Valuable methods and 

 results are given on the measurement of the sonorous eftects produced 

 by different substances, and also upon the nature of the rays that produce 

 them. Bell adopts Mercadier's name, radiophone, and has studied the 

 spectrum to determine the active rays. The instrument eraplojTd he 

 calls a spectrophoue, and the results obtained with it are given in a 



