Humboldt State University
Robert A. Paselk Scientific Instrument Museum
Wm. Gaertner & Co. ?
Humboldt S-T-C ?; c. 1930
Used for examining crystals, quartz, mica, optical glass etc. in polarized light. With the use of the accessory tube and holder it can also be used as a polarimeter (though a rather inaccurate one) for measuring the polarization of optically active liquids. In this instrument the light is polarized using a tiltable glass plate (missing) above the mirror. The light may either be reflected directly to the specimen, or down to the mirror and then passed back through the plate to the specimen, and then to the nicol prism analyzer. Alternatively a black glass or pile of plates analyzer may be used. Both the specimen stage and analyzer are mounter in graduated circles to read the degree of polarization. The identical instrument, including description and illustrations, but with additional accessories available, is shown in Gaertner catalog for 1927, the instrument thus appears to be a Gaertner product. The catalog scan is from: Braun-Knecht-Heiman-Co. Catalog No. 29 Laboratory Apparatus and Chemicals for Physics - Chemistry - Biology - Agriculture - General Science as required for Educational Purposes. San Francisco. (1929); it is used by permission.
The instrument is incomplete, consisting of a series of loose components mounted on a new half inch aluminum rod and cast iron stand. There are two graduated (0-90-0-90-0 degrees by 5 degree increments), rotating, brass stages with 2 3/16" (55 mm) openings to accommodate windows etc. held in place by stage clips. The stages are held in cast brass mounts. Currently each has a brass disk with a centered eyepiece mounted Nicol prism (one large and one small, held in cork); three 1 1/2" dia. lenses of varying focal length in cast brass mounts; one #47183 tube holder with 47180 20 cm solution tube, and one 3 1/4" mirror in a cast brass mount. The lenses and collars have 0.5" sleeves and thumb nuts to clamp onto a 0.5" rod. The tube holder uses a standard 'v' type clamp as seen in lab clamps to mount onto the rod. All cast pieces are finished in black crinkle enamel paint. Machined brass parts (eyepieces, stages) have a chemically darkened finish.