INFLUENCE OF LIGHT ON THE PROPAGATION OP SOUND. 



3J 



an hour best adapted by the darkness of the weather to 

 show the effect of the absence of light. 



The olace of the experiment was lighted by a watch lamp 

 of a particular construction, which afforded light enough to 

 perceive the motion of the paper o.i the string, without the 

 rays being able to diffuse themselves through the chamber. 



The 



followin 



g were 



the resu 



Its. . 





Sept 



1803 



Therm 



omet-r. 



Barom- 

 eter. 



Hygro- 

 meter. 



Phono- 

 meter. 



Observatiens. 



20 



53-24° 



29-79 



65 



98-1 



11 o'clock a pight. The sky 

 covered with cJouds 



I was satisfied with this trial. Eager to make it public, 

 I spoke of it to some friends, who encouraged me to repeat 

 these trials, and to attend particularly to this subject, which 

 might prove highly interesting to the progress of science. 

 Private affairs prevented me from prosecuting it at that 

 time, and I did not resume it till about ten months after. 

 The following are the results of the experiments then made, 

 which tended only to confirm the preceding. 



Jul) 



1804. 



Therm- 

 ometer. 



Barom- 

 etL-r, 



Hygro- 

 meter. 



Phono- 

 meter. 



Observatiens. 



3 



66-2 



28'89 



73-5 



100 



About noon. The sky free 

 from clouds. 



5 



55 



28-90 



66-5 



97-5 



Quarter after 1 1 at night. The 

 sky partly covered with cloud*. 



U 



57 



29-86 



68 



99-8 



I o'clock afternoon. The wea- 

 ther fine. 



14 



62-24 



29-87 



51-5 



99-4 



Quarter after 1 P. M. Rain- 

 ing. 



18 



74-66~ 



28-90 



62 



98-4 



Just after midnight. The sky 

 cloudy. 



Table of com- 

 parative ^expe- 

 riments. 



Such have been the constant results of my researches. General con- 

 The mean term of the degrees of propagation of sound elusion, 

 ^vithout light in three different trials was found to be 0'98. 

 D 2 The 



