48 Proceedings of Royal Society of Edinburgh. [sess. 
sound, which lasts as long as the circuit is kept closed. The 
pitch, loudness, or quality of the sound may he modified by varying 
the strength of the battery current, by changing its direction, or by 
varying suddenly the length of the column of air, or the pressure, 
in the flexible tube (see diagram). 
Measurements made for me by Mr Alexander Galt, of the 
Physical Laboratory of the University of Glasgow, showed the 
resistance of the receiver (the electro-magnet) to be 2 ohms, while 
that of the variable resistance fluctuated between 13 and 29 ohms. 
The apparatus works well with two of Obach’s dry cells, Q pattern, 
which, with the resistance just mentioned, give about one-fifth of 
an ampere. 
The apparatus is interesting, not only on theoretical grounds, 
but because it suggests the possibility of constructing a new kind 
of musical instrument. Thus diaphragms might be tuned to the 
notes of the scale, and by pressing on keys, and thus completing 
circuits, musical notes having something of the quality of those of 
brass instruments might be produced. Possibly, also, by piercing 
holes at proper distances in the flexible tube, these holes might be so 
fingered as to produce different sounds, and thus we might have an 
electric flute. I have found a modification of Mr Graham’s method 
of great service in connection with the phonograph. It might 
also be adapted to the purpose of rendering audible in a room the 
sounds of respiration, or even the sounds of the heart. 
