770 Transactioits of the American Institute. 



The present communication is confined, however, to Koenig's 

 reflected flames, in which are seen the individual vibrations of an 

 organ pipe; by which can be beautifully demonstrated to the eye: 

 First, that the number of vibrations increases with the audible 

 pitch; second, that coexisting vibrations laroduce maxima and 

 minima of motion corresponding to the beats which are recog- 

 nized by the ear; third, that one column of air will respond, in 

 sympathetic vibration, to another when there is an agreement 

 between their fundamental notes or some of their harmonics; 

 fourth, that two unison-pipes, brought into intimate neighborhood, 

 will move so that the vibrations of the air cross one another and 

 produce silence, as Savart showed experimentally in the case of 

 pendulums of equal length vibrating in company. 



This peculiar case of unison-pipes I have made a subject of 

 special investigation. In complex cases, it would doubtless be impos- 

 sible so to arrange the voices and instruments that the total volume 

 of sound should be multiplied in the same ratio as the number of 

 performers. The effect of a large chorus or a large orchestra will 

 disappoint expectation, from the unavoidable interferences of sound- 

 waves. But in the simple case of ivio unison-pipes, can they be 

 prevented from silencing each other? The remedy for the evil 

 would be: First, to sacrifice in a measure the perfection of the 

 unison; or, second, to place them at a distance beyond each other's 

 influence; or, third, to separate them by one-half of the wave-length 

 which propagates a sound of the given pitch, or by some odd mul- 

 tiple of that quantity. The latter remedy would answer for audit- 

 ors in the direction of the line which united the two pipes, though 

 not for the audience generally. In studying the eflfect of position, 

 I have made the following experiments, the ear being the judge; 

 or the eye, looking at the broken ribbon of light in the revolving 

 mirror. 



I. The pipes are placed side by side by side. 



1. With similar ends together, they silence each other. 



2. With dissimilar ends together, they silence each other. 



n. The pipes are placed with their axis upon the same straight 

 line. 



1. If similar ends are together, whichever of the two ends be 

 selected, they silence one another. 



2. If dissimilai' ends are together, they silence each other. 

 ITT. The pipes are placed at right angles to one another, with 



one extremity of each pipe at the angle. 



