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Humboldt State University ® Department of Chemistry
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Usage/History: Used to experimentally demonstrate/verify the laws of composition and resolution of forces via vector addition and subtraction.
Description: The instrument has a 15.5" diameter cast aluminum plate, 0.5" thick at the rim, with reinforcing ribs beneath. There is a machined, slightly raised rim 1.5 inches wide around the outside on which a 360° engine divided scale is inscribed. The inner portion of the plate is black crinkle-finished, with a nickel-plated brass insert with a 0.25" hole in the center. The plate is held on a 1 1/8" diameter steel rod which threads into a heavy cast-iron tripod base with nickel-plated brass leveling-screw feet on each leg. The rod and base are finished in heavy black enamel. The tripod legs of the base are 8.5" long. The overall height (minimum) is 17". A brass tag is pinned beneath the rim near the outer edge: HUMBOLDT S-T-C 2689. There is a Cenco decal on one of the tripod legs.
The unfinished aluminum on the rim and edge of the plate were heavily corroded when the instrument was acquired. The corrosion was removed by rubbing with fine steel wool and Briwax, followed by polishing with a soft cloth. The painted surfaces were cleaned by vigorous rubbing with a cloth and Briwax, then polished with a soft cloth. There is some flaking of the crinkle finish on the plate, and some chipping of the enamel on the stand
Research: An apparently identical instrument is shown as item No. F1005 on pg 89 of 1929 Cenco Catalog F-129. An identical illustration and the same written description, with minor variations, is shown as item 74285 on pg. 1038 of the 1941 Cenco catalog J-141 (illustrated in this museum). The same instrument was still offered by Cenco in 1994, the only apparent change being the use of plastic knobs on the leveling screws instead of the metal cross-piece handles.
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