SENSITIVE FLAMES. 
159 
tive. However loud a note may be, if below a certain pitch, 
it will have no effect on the flame. This influence of pitch is 
well illustrated by running up the scale of a piano-forte ; the 
bass notes do not disturb the flame in the slightest ; but, as the 
high notes are approached, the flame becomes uneasy, and at 
last diverges strongly, when the third octave in the treble is 
reached. The strings in this octave make from 2,000 to 4,000 
vibrations a second. Moreover, the note which exercises the 
most influence on the flame, is not the same for all burners. 
I have in my possession a series of glass burners, each of which 
gives sensitive flames ; the orifices are of different sizes, and the 
flames are variously influenced by whistling the notes of the 
gamut. It appears that the smaller the orifice in the burner, 
the higher is the pitch of that note which most powerfully 
affects the flame. And, I have no doubt that, by means of a 
large and proper orifice and low pressure, a flame might be 
made responsive to grave sounds. 
With differently shaped burners effects complementary to those 
previously described have been obtained. Thus, the original 
flame may be of a fish-tail appearance, like fig. 2 in the plate. 
At the sound of a whistle, the flame rises into the tall, smoky 
flame shown in fig. 1, sinking back into the forked and flat 
shape the moment the sound ceases. It was an incipient effect 
of this kind that was noticed by Dr. Leconte in his fish-tail 
burner. With a large sized batswing burner the phenomenon 
is rendered more striking. The beautiful sheet of flame which 
this burner gives is split up into numerous tongues, at the sound 
of a whistle. This change is represented in fig. 2 : a is the 
quiescent flame, b the same flame, under the influence of the 
sound, thrusting out its fiery fingers.* 
* This experiment is Dr. Tyndall’s, to whose kindness I am indebted for 
the drawing from which this cut is taken, it being one of the illustrations 
in his forthcoming book on “ Sound.” To that work the reader is referred 
a 
b 
Tig. 2. 
