Ibi 24 Mr Mines, Note on the respiratory movements I 
prevent this little lever from falling by its own weight, and at 
the same time brings it into electrical connexion with the insu- 
lated binding screw C. The extremity of the second lever is bent 
back on itself so as to form a pair of jaws which pass on either 
side of the first lever, about 15 mm. from its axis. To the upper 
Jaw is fastened a small piece of platinum wire, which can make 
contact with another piece of platinum wire fastened to the main 
lever. The under jaw is prevented from making contact with the 
first lever by a thin piece of mica. The amount of play between 
the recording lever and the jaws of the second lever is made as 
small as possible consistent with the making and breaking of — 
contact with each up and down movement of the levers. This — 
arrangement provides for a rubbing contact between the platinum 
pieces. D is a stop. 
During the ascent of the recording lever, electrical contact is 
maintained between the binding screw C and the brass support; 
during the descent of the lever, the contact is broken. This holds 
good for a wide range of positions of the recording lever, and the 
arrangement will work even when the amplitude of the excursions 
is very small: it is limited, of course, by the width of the gap 
between the jaws of the second lever. This lever is connected to 
a source of current of about 4 volts and to the coils of a light 
relay. To obviate any sparking at the contacts a shunt may be 
introduced. ‘The intermittent movements of the relay actuate 
another cirewit which controls the apparatus shown in Fig. 2. 
This consists of a toothed wheel (a small circular saw was used) _ 
which is moved on, one tooth at a time, by a ratchet actuated by 
an electric magnet. A difficulty in the construction of an electric 
counter is that the movements of the armature of the magnet are 
apt to be so abrupt that the wheel may be shot on more than one 
step at a time. This difficulty is overcome by the use of a 
glycerine brake, which is seen below the toothed wheel. The 
ratchet actuating the wheel and that preventing it from slipping 
back, are placed near together on the periphery of the wheel. A 
second electro-magnet # is so arranged, that when it is energised 
both these ratchets are pulled away from the toothed wheel, so 
that it is free to move. On the same axis as the toothed wheel is 
a small grooved pulley, on which is wound a piece of silk thread. 
The other end of the thread is attached to a suitably weighted — 
lever. The wheel is furnished with a stop so that when the 
magnet H is energised, the wheel and the lever return to a 
definite zero position. The magnet H# is excited for a period of 
eight seconds once a minute, the circuit being made by a wire 
connected to the second-hand of an ordinary clock dipping into a 
pool of mercury contained in a cavity in a paraffin block on which 
the clock stands. 
