To relieve the artisan from the fatigue of holding the magnifier in the eye-socket or in the hand, a stand with a moveable socket is sometimes resorted to, such as that represented in fig. 8. A horizontal arm slides upon a vertical rod, upon which it can be fixed at any desired height by a tightening screw. This arm consists of two joints, connected together by a ball and socket, by which they can be placed at any desired inclination; at the extremity of the lower arm a fork supports a ring-shaped socket, made to receive the magnifier.
Advertisment from the Journal of the Royal Microscopical Society, 1880
(Note the red arrow)