The Microtropometer

Abstract

MANY roads to progress in physical investigation are brought to an abrupt end through the lack of measuring instruments of sufficient sensitiveness. In the attempt to bridge over one of these disabling chasms the writer was led to the following device, which appears capable of some development. The principle can be illustrated with reference to a particular case. Suppose we have a Boys's radio-micrometer, which we will call the secondary instrument. If we project on to the vane of this an image of a Nernst lamp filament the beam of light from the mirror of the instrument may be deflected through one thousand scale divisions. Suppose now that the image of the filament is 1 mm. wide, and that it is projected by the mirror of another radio-micrometer, which we may call the primary one.