326 Dr. A. M. Mayer on a Method of defecting the Phases 



Applications of the Method. 



When the method I have here marked out shall have been 

 reduced to the refinement it is susceptible of, I feel confident 

 that we shall thereby have the means for attacking many 

 problems of high theoretic interest which have heretofore been 

 deemed beyond the reach of experiment. Its applications to such 

 are so numerous that they are almost coextensive with the 

 phenomena of sound. 



The actual experimental determinationof wave-surfaces in free 

 air and in buildings can now certainly be accomplished; and 

 such determinations may serve to extend our knowledge in the 

 direction of giving the proper laws which should govern archi- 

 tects in their construction of rooms for public assemblies. 



Without any consideration of the velocity of sound or of the 

 number of vibrations pertaining to a given note, we can accu- 

 rately measure the wave-length of the note by the following simple 

 arrangement of apparatus. Take an organ-pipe and a resonatoi* 

 in unison with it, and place the resonator in a fixed position 

 opposite the mouth of the pipe ; then lead a gum tube from the 

 resonator to a manometric capsule whose jet is contiguous to 

 the jet of the organ-pipe, and adjust the flames to coincidence 

 ,of serrations, using for that purpose the manometric micrometer. 

 Now suppose, for simplicity, that the pipe gives 340 complete vi- 

 brations in one second; then, as the velocity of sound is 340 metres 

 per second, it will take ■^^-^y of a second for an aerial pulse to tra- 

 verse 1 metre. Therefore, if the resonator-tube be lengthened 

 ^ metre, the serrations of its flame will no longer coincide with 

 those of the pipe, but will bisect the spaces between the latter ; 

 for an impulse in the resonator-tube has now to travel such an 

 increased length that it arrives at the manometric flame -g-^-g- 

 of a second later than before the tube was lengthened. If the 

 tube be lengthened 1 metre, or a wave-length (English), the dis- 

 placement of the resonator- flame will amount to the entire distance 

 separating the centres of two contiguous serrations ; and for n 

 number of wave-length elongations of the tube we shall have n 

 number of such displacements. Thus can be measured not only 

 one but very many wave-lengths ; for the intensities of the pulses 

 I have not seen sensibly diminished after having traversed many 

 metres of firm thick tubing; and hence, the errors of measure- 

 ment being divided over so great a distance, the accuracy of the 

 determination of a single wave-length is much increased, espe- 

 cially when the determinations are made in connexion with the 

 manometric micrometer. If the number of vibrations given by 

 the pipe can be determined with a proportionate accuracy, we 

 shall succeed in arriving at precise measures of the velocity 



