Vernier Synonyms

The latter are in fact little microscopes carrying a vernier etched on glass, in lieu of a filar micrometer.

A micrometer drum reads to 2', while the vernier reads to single minutes so that very fine adjustments can be made.

If we now attach to the polar axis a graduated circle D D, called the" hour circle,"of which the microscope or vernier R reads o h when the declination axis is horizontal, we can obviously read off the hour angle from the meridian of any star to which the telescope may be directed at the instant of observation.

A slight rotatory motion of the telescope E on its axis enables the vernier of the declination circle to be read through prism 1.

The polarizing prism is fixed at the centre of a circular disk, that has a scale on its circumference, which with a fixed vernier determines the positions of the polarizer, for which the bands disappear at the assigned point of the field.