1 10 Dr. R. Konig on Manometric Flames. 



its violent flickering, the existence of beats, which are also heard 

 distinctly. 



I draw particular attention to this isolated occurrence of the 

 resonance-vibrations in the air-column, because it is not exhi- 

 bited by the influence-phenomena of two strings stretched above 

 the same sounding-board; but the proper vibrations combined 

 with resonance-vibrations appear in the string influenced, with- 

 out its being struck or bowed. 



It is known that the beats of two such mutually sympathetic 

 strings accommodate themselves to each other in such a manner 

 that the one reaches the maximum amplitude of its vibrations 

 when the other is at the minimum. Now the flames of the two 

 sympathetic organ-pipes exhibit the same phenomenon, for as 

 the one rises the other falls ; both, however, must be blown at 

 the same time, whilst it is only necessary to play on one of the 

 strings. 



When the pipes are in perfect unison, and their single vibra- 

 tions mutually adapt themselves in the same way as the beats 

 did, i. e. that in the node of the one there is a condensation of 

 the atmosphere when in the other a rarefaction takes place, then 

 the whole process can be clearly observed in the two flames if 

 we place them one beneath the other in a vertical line. Both 

 flames show their vibrations unweakened; yet their individual 

 pictures in the rotating mirror are not beneath each other in 

 the two lines, but alternate. 



If both notes act together on the same flame, they, of course, 

 at the beats show more violent flickerings than did the two 

 flames ; for the latter were produced by direct and by sympathetic 

 and therefore unequally strong vibrations in the same air-column, 

 whilst the present ones are formed by direct and therefore nearly 

 equally strong notes in two similar air-columns. If the two 

 notes are approximated gradually to unison, we observe that the 

 oscillations cannot be made slower at will, as with tuning-forks, 

 but at a certain limit they disappear suddenly, and both air- 

 columns vibrate as one system, i. e. as two somewhat differently 

 tuned bodies that are so closely united and therefore act so 

 strongly on one another that neither can give its proper note in 

 its integrity, and the consequence is that only a single interme- 

 diate note is produced. This note is more powerful than that of 

 a single organ- pipe ; and the flame shows in the centre of its 

 interior a brilliant waist, which rises above a non-brilliant blue 

 broad hollow space. As it approaches perfect unison more 

 and more, the height of this dark space increases, the brilliant 

 waist vanishes ; and when unison is attained the flame appears in 

 complete repose. At the same moment the strong fundamental 

 has almost disappeared, and we hear the first overtone clearly 



