IjfFLUENCE OF LIGHT ON THE PROPAGATieN OF SOUND. 



eiices ill tlie propagation of sound, was exxecuted on the 14th 

 of May, 1803. 'lukiug the precaution to unite the nieteo- 

 roloj^'ical observations uith the indieatioas of my apparatus, 

 1 noted in my pocketbook the degrees of the diti'erent in- 

 struments I employed at the nioment of the experiment. 

 The weather was calm an<l clear, and the sun shone into my 

 room. The following are the lesults and uieteoroiogical ob- 

 servatio'.is of thid first trial. 



33 



May 



Thermo- 



Barom- 



Hvgto 



Appa- 





1803. 



meter. 



eter. 



mefer. 



ratus. 



Observntions. 





ir 



28-408 



3^i 



100 



rills exr)eiinient, begun 



14 



51-8°F. 



30-28 E. 







at 20' after noon, was 

 repeated several times. 

 My apparatus always 

 marked the same dis- 

 tance to a few thou- 

 sandths. 



Trial of it. 



The whole of the scale of my phonometer, which is the its scale, 

 name I give my apparatus, answers to 2 met. 14 cent. [7 feet], 

 and consequently each degree is equivalent to about 2 cent, 

 [8 lines]. 



This done, to proceed methodically I conceived it riorht to 

 lay down as a fixed principle, that the distance of 7 feet was 

 the limit of the greatest propagation of sound in my appa- 

 ratus under the influence of light. 



I was now eager to repeat these experiments in the dark, Might not the 



in order to clear up mv doubts of the difference there mieht ^^'^^^^ of other 

 ' - . ^ causes be con- 



be in the velocity and propagation of sound by night and by founded with 



day. The apparatus 1 employed promised me results suf- '^^'® ^^ light? 

 ficiei.tly conclusive from the length of its scale, and light- 

 ness of its motion. It appeared to me, that the least vari- 

 ation must be perceptible, and capable of strict proof, when 

 I could depend on my own attention, and the niceness of 

 my ear. One difficulty only presented itself to my mind, 

 which arose from the influence, that variations in the tem- 

 perature, weight, and humidity of the atmosphere might 

 have on the phonometrical changes. I was aware, that the 

 propagation of sound must be according to the nature and 

 density of the elastic fluids it traverses; and I was appre- 

 |i€nsive of being led into errour by a cause foreign to that 

 Vol. XXV. Jan. 1810. l> >vhicU 



