350 



APPENDIX. 



a thin vertical needle is attached to it at the place 

 where the weight hangs in the Figure, at the end of 

 the needle is fixed a small piece of cork which rests 

 on the ventricle, the frog lying on a stage below the 

 lever. 



Time Marker. 



The two ends (w, w') of the wire wound round the 

 bobbins (b, b') are connected with the binding screws 

 (sc, sc'). In using the instrument one binding screw 

 is connected with one of the poles of a galvanic 

 battery, the other binding screw with a clock or 

 metronome from which runs a wire to the other pole 

 of the battery. The clock or metronome is arranged 

 so that it makes and breaks the circuit at regular 

 intervals. When the circuit is made the current 

 passes round the bobbins, the soft core of the bobbins 

 becomes magnetized and the lever (I) is drawn down ; 

 when the circuit is broken the lever is drawn away 

 from the bobbins by the spring (sp). At the end of 

 the lever is fixed a stiff bristle (to write on smoked 

 paper) or a small bent glass tube filled with magenta 

 dissolved in dilute glycerine (to write on glazed 

 paper). 



FIG. 6. 



