[ 541 
LXI. Acoustic Experiments. By Count Scuarrcorscn*. 
GLASS tube open at both ends, when simply blown upon 
by the mouth, gives its fundamental tone, ?. e. the deepest 
tone belonging to it, as an open organ-pipe, feebly but distinctly. 
On placing the open hand upon one of the openings and rapidly 
withdrawing it, the tube yields two tones one after the other ; 
first the fundamental tone of the closed pipe, and then the tone 
of the open pipe, already mentioned, which is an octave higher. 
By the application of heat these fundamental tones, of which 
only the higher one will be taken into consideration here, are 
raised, as is well known; this is observed immediately on blow- 
ing upon a tube heated externally, or by a gas-flame burning in 
its interior. For example, a tube 242 millims. in length and 20 
millims. in diameter, heated throughout its whole length, when 
blown upon even before it reaches a red heat, gives a tone raised 
a major third, namely the second G sharp in the treble clef, 
instead of the corresponding B. Ifa gas-flame 14: millims. in 
length and 1 millim. in breadth at the bottom, is burning in 
the tube, the tone rises to the second treble F sharp. The same 
gas-flame raises the tone of a tube 273 millims. in length and 
2] millims. in width, from the second treble D to the corre- 
sponding E. These two tubes, which for brevity will hereafter 
be referred to as the H-tube and the D-tube, served for all the 
following experiments, the object of which was to show a well- 
known and by no means surprising fact in a strikimg manner, 
namely that the column of air in a tube is set in vibration when 
its fundamental tone, or one nearly allied, for example an octave, 
is sounded outside the tube. The existence of the aérial vibra- 
tions was rendered perceptible by a column of smoke, a current 
of gas, and a gas-flame. 
1. A glimmering smoky taper was placed close under the 
B-tube held perpendicularly, and the smoke passed through the 
tube in the form of a uniform thread. At a distance of 1°5 
metre from the tube, the first treble E was sung. The smoke 
curled, and it appeared as if a part of it would be forced out at 
the upper, and the other part at the lower opening of the tube. 
2. Two gas-burners, 1 millim. in the aperture, were applied 
near each other to the same conducting tube. Common gas 
flowed from both of them; one projected from below into the 
D-tube for about one-fifth of its length; the gas-flame of the 
other was 3 millims. in height. Ata distance of 1-5 metre there- 
from, the first treble D was sung; the flame instantaneously 
increased several times in breadth and height, and consequently 
: eh the Monatsbericht der Kinigl. Akademie 2u Berlin for April 30 
857. 
