Holometer of Brunel

This instrument has a black wooden case painted to resemble a book. On the inside is a paper scale in the shape of an octant (eighth of a circle), screwed to the case, with the center of the circle at the front left corner. A metal arm that pivots on this center has a plastic indicator at the opposite end. Scales lettered from A to N that are marked near the circumference. The scales represent tangents, cotangents, sines, cosines, the division of an arc of a circle into differing numbers of equal parts, lengths of the sides and areas of inscribed polygons, areas of the faces and volumes of inscribed polyhedra, and proportions of ellipses. Across the bottom edge are two linear scales, one of centimeters divided to millimeters and one of inches divided to lines (twelve lines/inch).

The holometer was an invention of the French nobleman Louis-Clément de Brunel de Varennes who spent many of his formative years fighting Napoleon’s army. The engraving of the scales was done by Pelicier. Brunel envisioned the instrument as a replacement for the sector, particularly useful in design.

The instrument was noted in contemporary journals but does not seem to have become common.

References:

L.-C. Brunel de Varennes, Métroscopographie, ou Nouveau système de perspective, Paris: Bachelier, 1830.

J. W. Woollgar, “Description of the Holometer,” Mechanics Magazine, vol. 14, September 18, 1830, pp. 40-42.

Currently not on view