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.
Maurice Daumas, Scientific Instruments of the Seventeenth and Eighteenth Centuries, English
trans. by Mary Holbrook (New York, 1972), p. 100 and 282.