CHAPTER II 



THE RESONANT RECORDER 



Advantages of intermittent contact in record — Two types of apparatus : 

 the Oscillating Recorder and the Resonant Recorder — Coercer and 

 Vibrator — Perfect tuning — Recorders with standardised frequencies — 

 Slide and clockwork — The record its own chronogram — Smoked 

 surface and its fixation — Adjustments of the writer — Records with 

 continuous and intermittent contacts. 



It was stated in the last chapter that however Hght the 

 contact may be, and however smooth the glass recording- 

 surface, the record was still apt to be either arrested, or 

 seriously distorted, on account of friction. As long as I 

 employed the ordinary method of continuous contact of 

 the writing-point with the glass surface, it was impossible 

 to overcome this particular difficulty. It occurred to me at 

 last that the problem might find a solution if I could succeed 

 in making an intermittent instead of a continuous writing- 

 contact. I have solved this problem by devising two 

 different types of apparatus, which I have called respectively 

 the Oscillating Recorder and the Resonant Recorder. In 

 the former, the recording-surface itself is made by an 

 electro-magnetic device, to vibrate to and fro, thus bring- 

 ing it into periodic contact with the writing-point. ^ This 

 apparatus is extremely convenient for the general pur- 

 pose of recording responses in which the measurement of 

 excessively short intervals of time is not essential. 



But there are many important problems, such as the 

 determination of the latent period, and accurate determina- 

 tion of the velocity of transmission of excitation, in which 



^ Bose : British Association Report , Dublin, 1908, p. 903. 



