6 Dr. R. Konig on Manometric Flames. 



ever, if we make the two capsules of the two corresponding organ- 

 pipes act on the same flame. 



If we sound two organ-pipes, exactly tuned to an octave, 

 while the gas streams from their two capsules into the same 

 burner, the flame has the appearance of containing within it a 

 smaller one without motion. By the slightest discord, how- 

 ever, the latter becomes flickering, and lengthens and shortens 

 periodically within the greater one. Each of these double 

 movements composed of ascending and descending shows a 

 fluctuation, either the deviation of the upper tone by a 

 double vibration, or of the lower by a single vibration from the 

 pure interval of the octave. 



The fifth (2 : 3) shows three, the fourth (3 : 4) four, the third 

 (4 : 5) five points of flame one above another, whose mutual 

 position remains unchanged with the perfect purity of the in- 

 terval ; on the contrary, any deviation from this causes an up- 

 and-down movement among them of each single point, which 

 takes the appearance of a waving motion. 



In all these intervals it is easy so to arrange the length of the 

 flame that all the points may remain clearly bright and appear 

 separated from each other by blue non-luminous parts of the 

 flame. If, however, the ratios of vibration of the two tones 

 becomes more complicated, it is often difficult to observe them 

 exactly ; but even in this case the flame shows plainly whether 

 the interval be pure or out of tune, as we have but to see whether 

 the flame is at rest or in motion. 



This property of the manometric flame, of showing the least 

 deviation from the purity of the interval, makes it in many 

 cases exceedingly useful in tuning, as it is not necessary that 

 the two notes which are to be brought into tune should be 

 produced by organ-pipes provided with capsules : the notes of 

 any instrument may be used, if they are produced before two 

 resonators in relation with them, which act on two manometric 

 capsules whose gas-pipes end in the same burner. 



The ratio 1 : 2 is the most convenient, on account of its easy 

 examination ; so that if we want to tune a series of tuning-forks 

 to the same note, it is better to choose the fork for comparison 

 an octave lower or higher. 



If we wish to observe the whole process of vibration in the 

 above-mentioned flames on which two notes act at the same 

 time, we must again employ the rotating mirror. The pure 

 octave shows in it a series of flames, in which a shorter always 

 follows a longer, and the shorter ones have all, like the longer 

 ones, equal heights (fig. 4, PL I.). If any beats occur, the 

 summits of the smaller as well as of the larger flames move up 

 and down. However, these motions are opposed; so that in 



