TRANSMISSION OF SOUND THEOUGH LONG TUBES. HI 



air. The sound through the metal alone was perceptibly at all through 

 transmitted. Lastly, thouajh we could still hear the sound * ^ *"' 

 of the voice, it was not sufficiently clear for us to distin- 

 guish words, or to transmit the necessary information after 

 fOttr observations. From the gr^ut difficulty, which Messrs. 

 Malus and liouvard had already experienced at a, much 

 «horter distance, we: were all inclined to suppose, thiit we 

 had attained a distance, at which the human voice, even 

 the loudest, ceases to be distinguishable in pipes. 



;, However, the extreme facility with which we heard each But thisim- 

 other at 200 metres seemed to me to render so great a di- I'J^*'-*^''^ from 



T, . 1 . ihe 1st exped- 



oainution altogether inexplicable. Besides, in the mathe- mtnts, 



matical theory of the motion of air we find nothing to indi- and from th.e. 

 cate, that sound should be diminished in cylindrical pipes, *''")'• • 

 It appears on the contrary, that it ought to be transmitted to 

 an indefinite distance with the same intensity, deducting 

 merely the diminution, that the friction of the air against 

 the pipe might perhaps produce. To decide the question, 

 and know positively whether sound were weakened in such 

 an extraordinary degree, I resolved to remove or diminish 

 all the cause* of foreign and neighbouring noises, that 

 might drown the sound I sought to hear. I went to the The experi- 

 place of experiment only with Mr. Martin and two intelli- ments repeat- 

 , J i_ i- xu • . xi. Ml ed m the dead 



gept workmen, and chose lor these experiments the stillest of night, 



hours of the night, those from one to four in the moruing. 



I then discovered, that my conjectures were well founded, when not only 



We not only heard the two sounds of the hammer and bell the sounds of 



,. . , , 1 . , , , , the bell and 



80 distinctly as to observe the intervals such as 1 nave re- hammer, but 



ported them; but even the lowest voice was heard so as ^he lowest 

 perfectly to distinguish the words, and to keep up a con- heard, 

 yersatioD on all the objects of the experiments. I wished to 

 determine the point at which the voice ceases to be audible, 

 but could not accomplish it : words spoken as low as when 

 we whisper a secret in another's ear were heard and under- 

 stood ; so that not to be heard there was but one resource, 

 that of not speaking at all. 



From this experiment there can be no doubt, that words 

 may be transmitted so as to be distinctly heard at a more 

 considerable distance. Between a question and answer the 

 interval was not greater, thaa was necessary for the trans- 

 mission 



