Mr. F. W. Barrett on Sensitive Flames. 217 



down several inches, at the same time spreading out sideways 

 into a flat flame, which gave an increased amount of light from 

 the more perfect combustion of the gas. Having drawn Pro- 

 fessor TyndalPs attention to this influence of certain notes on a 

 naked gas-flame, with his consent I followed up the observation 

 by a short investigation, of the results of which he was unaware, 

 with a view to ascertain the cause and exalt the action of this 

 singular phenomenon. 



I subsequently heard that a somewhat similar but reverse 

 effect to that which I had observed had been noticed in America, 

 and for the first time read the details of these experiments in the 

 lecture to which I have referred. I was then made aware that 

 Professor Leconte had noticed (in 1858) that musical sounds 

 caused the spasmodic jumping of a fish-tail gas-flame, and had 

 made the happy observation that the flame did not jump until 

 the pressure of the gas caused it to be near flaring. Having 

 submitted Professor Leconte's discovery and my own simple ob- 

 servation to a careful examination, Professor Tyndall incorpo- 

 rated the results in his elegant lecture demonstration of January 

 the 18th last. 



As, however, that lecture dwelt almost entirely upon the action 

 of sounds on gas-flames rendered sensitive by increasing the 

 usual gas-pressure, which, with many, introduces a difficulty in 

 the repetition of the experiments, I have thought it worth while 

 to publish the following brief record of my experiments, made 

 with gas burnt direct from the main. The experiments for the 

 most part were executed at my own home, during the months of 

 June and July 1 866. They will be found to add but little, if any- 

 thing, to the comprehensive paper published by Professor Tyndall. 



The general effect noticed is as follows. A gas-flame burning 

 from the tapering jet, B, fig. 1, gives the appearance represented 

 in that figure. It is a dull quivering flame, throwing off clouds 

 of unconsumed carbon. When a shrill note is uttered or played, 

 this flame at once shrinks in height and spreads out in width, 

 taking the shape shown in fig. 2. In the first figure the flame 

 has a loose and ill-defined shape ; in the second it has, as it 

 were, a certain degree of tension, with a flat divergent appearance, 

 thick at the edges. To naked flames capable of responding 

 by their motion to certain sounds Professor Tyndall has given 

 the name of sensitive flames ; by this expressive word they will 

 in future, I trust, be designated. When a sensitive flame is 

 spread out under the influence of sound, I will term it in this 

 paper a divergent flame. It was noticeable that the divergence 

 of the flame did not reach to the burner, but under the main flat- 

 tening, a, fig. 2, was a small swelling, b, at right angles to, and 



