156 
POPULAR SCIENCE REVIEW. 
pressure of the gas, as indicated by the American physicist, 
enriched the experiments and brought the subject so under 
command as to raise them to the dignity of a Friday evening 
lecture at the Eoyal Institution. It was in this elegant lecture 
demonstration of January 18th last, that Dr. Tyndall gave at 
once the name and publicity to “ Sensitive Flames.” 
So much for the historical part of the subject. Let us now 
describe more in detail how gas flames may be rendered sensi- 
tive, and what they are capable of exhibiting when in this state. 
In my investigation of the shrinking flame the gas was used 
direct from the main. The flame burnt, therefore, under the 
ordinary pressure attainable by everyone. The most essential 
condition of success is the shape of the burner whence the gas 
issues. The one I found to succeed the best is shown in the 
annexed drawing, fig. 1, where it is represented of its real size. 
It is formed of a piece of glass tubing, about f ths of 
an inch across, contracted at one end to a tapering ori- 
fice -jL-th of an inch in diameter. This orifice must be 
slightly v-shaped, as shown in the figure. It is only 
the work of a minute to form such a burner. A short 
length of glass tubing, softened in a gas flame, is readily 
drawn out to a point, the extreme end of which must 
be broken off ; and the aperture can then be enlarged, 
and snipped into the shape indicated by means of a 
pair of scissors. Connecting this burner with the gas 
pipes, by means of some flexible tubing, it should be 
continually tested with the sound of a whistle whilst it 
is being trimmed into shape. I have always found this 
rough and ready mode of making the burner to answer 
very well. A more permanent burner can also be 
formed of a gas-fitter’s brass blowpipe, straightened and 
filed to a rather larger and v-shaped aperture ; or it 
^S * lm may be made of a bit of compo gas piping hammered at 
one end into a tapering orifice. A little patience and experience 
will soon bring success, of whatever material the burner be 
made. 
When any one of these properly shaped burners is connected 
with the gas pipes, the stopcock being fully open, a tapering 
flame about 15 inches long is obtained. The sound of a 
whistle, or the higher notes of a musical instrument, or even a 
noise, as clapping the hands or tapping the table, totally alters 
the shape and character of this flame. Immediately the sound 
is made, the tall quivering flame shrinks down nearly half its 
height, and spreading out laterally into a fish-tail flame, gives a 
largely increased amount of light, from its better exposure to the 
air. On the cessation of the sound, the flame again rises to its 
original height. The difference between the two flames is shown 
