506 Mr. W. H. Preece. On the Conversion of [Mar. 10 r 



upon them by twos and threes, and summits consisting of a refracting 

 spherule. This very difficult observation appears to open a new field 

 of research. The object upon which these beaded villi were first 

 detected is the scale of the Vanessa Atalanta, or Red Admiral. 



March 10, 1881. 



THE PRESIDENT in the Chair. 



The Presents received were laid on the table, and thanks ordered for 

 them. 



The following Papers were read : — 



I. " On the Conversion of Radiant Energy into Sonorous Vibra- 

 tions." By William Henry Preece. Communicated by 

 the President. Received February 21, 1881. 



Messrs. Graham Bell and Sumner Tainter* have shown that, under 

 certain conditions, intense rays of light, if allowed to fall with periodic 

 intermittence upon thin disks of almost every hard substance, will set 

 up disturbances in those disks corresponding to this periodicity which 

 result in sonorous vibrations. Mr. Bell has subsequently shown that 

 such effects are not confined to hard substances, but that they can be 

 produced by matter in a liquid form. y» 



These discoveries have elicited a considerable amount of interest, 

 and have led to the inquiry whether the sonorous effects are due, as 

 the discoverers themselves surmised, to light, or as the President of 

 the Royal Society, Professor Tyndall, and others have suggested to- 

 radiant heat. 



Messrs. Bell and Tainter have partially answered this question by 

 showing that the disturbances are not necessarily due to light, for they 

 found that sheets of hard rubber or ebonite — a substance opaque to 

 light — do not entirely cut off the sounds, but allow certain rays to 

 pass through, which continue the effect. M. Mercadier, who has 

 studied the subject with great care,f has shown that the effects are 

 confined to the red and ultra-red rays. Moreover, Professor Tyndall 

 has shown J that gases, such as sulphuric ether, which he had proved 

 to be highly absorbent of heat rays, while they are transparent to 



* American Association for the Advancement of Science. Boston, August 27,, 

 1880. 



f " Comptes Eenclus," tome 91, p. 929. 



J " Journal of the Society of Telegraph Engineers," vol. 9, p. 404. 



