Excerpt from An Essay on the Mechanism of the Ossicles of the Ear
The following measurements were made by means of an ocular micrometer. By turning the eye-piece round until the luminous lines ran exactly at right angles to the subdivisions of the micrometer, their lengths could then be readily measured. As far as possible they were taken from the same positions, namely, from above, as seen in Fig. 1, and from the side, as seen in Fig. 2.