Measures 1 The circles by Reichenbach, then almost exclusively used in Germany, were read by verniers only.
The word is used also to designate the supporting frame or arms carrying the microscopes or verniers of a graduated circle.
Repsold introduced essential improvements in the meridian circles by substituting microscopes (on Jesse Ramsden's plan) for the verniers to read the circles, and by making the various parts perfectly symmetrical.
The two verniers on the azimuth circle having been read, the magnet is then inverted, i.e.
The mean of all the readings of the verniers gives the reading on the azimuth circle corresponding to the magnetic meridian.