The analyser can be rotated, the angle being read by a divided circle F.
Thomson's tide gauge, tidal harmonic analyser and tide predicter are famous, and among his work in the interest of navigation must be mentioned his tables for the simplification of Sumner's method for determining the position of a ship at sea.
For examining preparations in polarized light a polarizer D is introduced n the illuminating apparatus below the diaphragm and an analyser E ai.
Very often the analyser is placed in the tube, a little above the objective: it is then generally in a case G, which can be put into the tube.
The placing of the analyser near the objective has the advantage that the field of view is not restricted, as is the case if the analyser .is used above the eyepiece.