A Device for Recording Photometer Settings
Charles P. Matthews · Physical Review · 1898
I N the ordinary photometric process, there occurs between successive settings a considerable interval, in which a reading of the bar is taken and recorded, either by the observer or an assistant.Various expedients for reading the bar are resorted to, as, for example, the use of a hand-mirror to reflect a beam of light from one of the sources, or the turning on of a glow-lamp.These methods are not free from objection.The sudden influx of light produces in the observer fatigue of the retina and of the pupillary muscles, and there is a consequent loss of visual sensitiveness.Furthermore, when it is a question of the photometry of a fluctuating source, the infrequency and irregularity of the readings is a drawback.In arc-light photometry the illumination of the photometer disk is a shifting quantity.Some means of recording a setting as soon