144 BULLETIN OF THE 



produced by masses, but would also permit us to test the more 

 general proposition that sonorousness, under the influence of inter- 

 mittent light, is a property common to all matter. 



The substance to be tested was to be placed in the interior of a 

 transparent vessel made of some material, which (like glass) is 

 transparent to light, but practically opaque to sound. 



Under such circumstances the light could get in, but the sound 

 produced by the vibration of the substance could not get out. The 

 audible effects could be studied by placing the ear in communica- 

 tion with the interior of the vessel by means of a hearing tube. 



Some preliminary experiments were made in Paris to test this 

 idea, and the results were so promising that they were communi- 

 cated to the French Academy on the 11th of October, 1880, in a 

 note read for me by Mr. Antoine Breguet.* Shortly afterwards I 

 wrote to Mr. Tainter, suggesting that he should carry on the inves- 

 tigation in America, as circumstances prevented me from doing so 

 myself in Europe. As these experiments seemed to have formed 

 the common starting point for a series of independent researches 

 of the most important character carried on simultaneously in 

 America by Mr. Tainter, and in Europe by M. Mercadier,f Prof. 

 Tyndall,| W. E. Ronton, § and W. H. Preece,|] I may be permitted 

 to quote from my letter to Mr. Tainter the passage describing the 

 experiments referred to : 



" Metropolitan Hotel, Rue Cambon, Paris, 



"Nov. 2, 1880. 

 " Dear Me. Tainter : * * * I have devised a method of 

 producing sounds by the action of an intermittent beam of light 

 from substances that cannot be obtained in the shape of thin di- 

 aphragms or in the tubular form ; indeed, the method is specially 

 adapted to testing the generality of the phenomenon we have dis- 

 covered, as it can be adapted to solids, liquids, and gases. 



" Place the substance to be experimented with in a glass test-tube, 



* Comptes Rendits, vol. xcl, p. 595. 



f" Notes on Radiophony," Cotnptes Rendtis, Dec. 6 and 13, 1880; Feb. 21 

 and 28, 1881. See, also, Journal de Physique, vol. x, p. 53. 



J" Action of an Intermittent Beam of Radiant Heat upon Gaseous Matter/' 

 Proc. Royal Society, Jan. 13, 1881, vol. xxxi, p. 307. 



\" On the tones which arise from the intermittent illumination of a gas." See 

 Amialen der P/iys. und Chemie, Jan., 1881, No. 1, p. 155. 



|| " On the conversion of Radiant Energy into Sonorous Vibration." Proc. 

 Royal Society, March 10, 1881, vol. xxxi, p. 506. 



