Page:Collected Physical Papers.djvu/385

Rh The friction of the writing point against the smoked glass surface, however, introduces serious error in the accurate record of the amplitude and time-relations of the response-curve. The difficulty has been overcome by the writer being thrown into resonant vibration in

consequence of which the record consists of a series of dots; the error arising from friction of continuous contact is thus completely avoided.

The Resonant apparatus consists of the writer, made of fine steel wire tuned in different cases, to vibrate