154 Scientific Proceedings, Royal Dublin Society. 
The aperture @ a is covered with a thin membrane of Indian 
rubber, such as is used for toy balloons, and is strengthened round 
its edges by a narrow strip of gold-beaters skin. 
A very light arm of aluminium J /, fixed by the screws s s, and 
having the small stud d upon it, is made to press lightly against 
the membrane, and carries at its end the marker m, which consists 
of a small and very fine sable brush. 
A continuous strip of paper is made to pass beneath the marker 
in the same manner as is employed in telegraphy. 
To provide for the escape of the air, a small orifice f is made 
in the tube of the mouthpiece. 
The pneumatic pressure exerted on the membrane is that due 
to the difference between the quantity of air forced into the 
trumpet in speaking, and that which can be delivered through 
the orifice in a given time. 
The strength of the spring of the aluminium arm and the 
size of the orifice in the tube require to be adjusted, so that, 
while the lightest pressures can be recorded, the movement due 
to the greatest pressures shall not exceed certain limits. 
When the object is to record whispering, or speaking, without 
recording the vowel sounds, it is sufficient to allow the small 
stud on the arm to press against the membrane. In this 
adjustment the instrument is very sensitive; so that in a long 
sustained action of breath the pulsations of the heart are shown. 
In order to record vowel sounds, the stud must be fastened 
to the membrane by gum or glue, and for the greatest development 
of this action, it is best to dispense with the aluminium arm 
altogether, and to glue a small marker directly on to the 
membrane. 
This arrangement is, however, not so good in other respects; in 
consequence of a lateral action which arises when the line of 
motion of the marker is not controlled by the arm. 
Some consonant actions, such as K and the hard G, have a 
negative pneumatic action, that is, the marker is first drawn 
towards the mouthpiece and then projected from it. 
If the marker is made to move in the plane of the paper it 
records all the movements. If the plane of the marker is inclined 
slightly downwards the connecting line at the bottom does not 
appear, and the syllables stand separate. In doing this, however, 
