The semicircle of this graphometer is graduated to single minutes, numbered clockwise
and counterclockwise, and read by verniers at either end of the alidade to 6 minutes. Meurand
worked as an instrument maker in Paris in the latter years of the 18th century.
Ref:
Maurice Daumas, Scientific Instruments of the Seventeenth and Eighteenth Centuries, English
trans. by Mary Holbrook (New York, 1972), p. 100 and 282.