
Mechanically Reinforcing Sounds. 287 
It would be unnecessary and tedious to describe all the 
experiments which led me to adopt the above arrangement, 
but there are one or two of interest that it may be as well to 
mention. If jet (a) in fig. 1 is used alone, the branches 
of the three-way piece Z being put into connexion with the 
air-bag and the gas supply respectively, a common blowpipe- 
flame can easily be obtained from (a), and this will be found 
to sing, but not nearly so loudly as the flame already spoken 
of : the blue tip of the inner cone can be seen shooting in 
and out as it emits the different sounds. If now a thin sheet 
of platinum-foil be brought into this part of the flame, the 
sound is very markedly reinforced, the tones given out by 
the hot platinum being very “ round,” smooth, and pleasant 
to the ear, though, as I have already said, they are not loud. 
I attribute this reinforcement to the rapid expansion and 
contraction of the platinum in response to the variation in 
the heat of the flame caused by the sound-waves from the 
phonograph, and not to simple reflexion of these waves from 
the platinum surface. The well-known surface action of the 
metal may also play some part in the phenomenon, although 
there is no reinforcement, if, whilst the platinum is in 
position and sounding, the blowpipe-flame is blown out: 
the platinum, under these circumstances, remains at a yellow 
heat, from the combustion of the unignited gas and air on 
its surface, but there is no sound until the flame is rekindled. 
Finally, the action of the flame in reinforcing sounds 
originally of equal loudness but of different pitch deserves 
notice. This can be generally stated as follows :—The 
smaller the flame the more rapid the current of air or of gas, 
or of both; or the more jet (6) is made to encroach on jet 
(a) in fig. 2 (0), the higher is the pitch to which the flame 
most readily responds and reinforces, and vice versd: but it is 
very remarkable how wide a range of pitch the tones may 
have which are reinforced at one and the same time, so that 
it is possible and easy in the case of a phonograph record in 
which the high-pitched notes have been recorded too strongly, 
to lessen their loudness, or, indeed, to eliminate them altogether 
without seriously interfering with the other notes: on the 
other hand, if it is the base which is too prominent, this may 
be reduced, whilst additional strength is added to the treble. 
I do not think that it is too much to say that these facts * 
* Note.—Since the reading of this paper, the writer has been much 
indebted to Mr. Chichester Bell for calling his attention to a communi- 
cation of Mr. Bell’s, read before the Royal Society, and published in the 
‘Transactions’ of that Society, 1886, Part 2, and entitled “The Sym- 
pathetic Vibrations of Jets.” It appears that as early as 1866 Kundt 
obtaimed musical tones by the impact of two flames, and of an air-jet 
