photometer

Prof. Zenger's differential photometer that we shall finally cite is an improvement upon Bunsen's.

The photometer, preferably one of the Lummer-Brodhun form, is set up on a gallery or bench.

There is no other way of measuring the exposure than by the photometer or personal experience, and the latter is by far the best.

A number of measurements of the illuminating power of an electric lamp were rapidly made during the lecture with this photometer.

An application of the law of intensity is made in using a simple (Bunsen) photometer.