Pocket Case of Drawing Instruments

This wooden pocket-sized case is covered with black sharkskin. Inside the lid is marked: Allen A. Jones. The set includes: a 3-7/8" brass semicircular protractor; a 4-3/4" ivory sector with a brass hinge; a 4-1/2" ivory plotting scale; 5-1/4" brass and steel dividers with a removable leg and separate pen point and crayon holder (containing a lead pencil whittled down to fit the holder); a 5" brass and steel drawing pen; a 3-5/8" brass and steel drawing compass with pen point; and 4-1/2" brass and steel fixed-point dividers. All of the pieces may be original except for the pencil.

The protractor is divided to single degrees and numbered by tens in both directions from 10 to 170. The plotting scale has diagonal scales at both ends. Above the plotting scale are scales divided to 1/10" and numbered by ones from 1 to 4, and divided to 1/12" and numbered by tens from 10 to 30. The back of the plotting scale has scales dividing the inch into 55, 45, 40, 35, 30, 25, and 20 parts and a line of chords.

One side of the sector has three double scales: sines, running from 10 to 80 degrees; tangents, running from 50 to 75 degrees; and a second tangent scale, running from 10 to 45 degrees. The outer edge of both legs has scales for logarithmic tangents, sines, and numbers. The top edge of the instrument has a scale divided to 1/12" and numbered by tens from 70 to 10.

The other side of the sector has a double scale along the fold line for regular polygons, from 12 to 6 sides. Both legs have scales of equal parts, running from 1 to 10 and labeled L; of secants, running from 40 to 75 and labeled S; and of chords, running from 10 to 60 and labeled C. The outer edge has a scale divided to 1/10" and numbered by ones from 9 to 1. Brass inserts protect points where users would frequently set divider points. The instrument is similar to sectors in the English style made in the mid-19th century. Compare to 1985.0580.06 and MA.333937.

Allen A. Jones, the husband of the donor, used this set in the U.S. Corps of Engineers during World War I and throughout his career as a civil engineer. He inherited the set from an uncle or great-uncle who the family believed had worked as a surveyor in the Chicago area prior to the 1833 founding of that city. The Smithsonian received the set in 1969.

Reference: accession file.

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