CD 1964043 E&MP26.035
August 19, 1936
How bright is a light?
The answer is no simple thing for intricate apparatus known as photometers are required to determine it. Great spheres, white on the inside, are placed around the lamp being measured and the total light, in all directions is integrated for its total value.
Shown above is such a device, opened up, at the lamp works of the General Electric Company