Signedinside: FOOTE, PIERSON & CO.
Inscribedback of instrument, stamped: Property of Harvard Engineering School
FunctionA photometer is used to compare the intensity (brightness) of two light sources. This instrument is aimed at an unknown source of light, which is then compared to the light found inside the instrument. The latter's intensity is varied by moving back and forth inside the instrument. It's position is recorded on the scale outside. It is based on this scale that the intensity of the unknown light source is determined.
For more information on how this particular type of photometer worked, see the following website.
ProvenanceFrom the Harvard Engineering School.