Gaertner Cathetometers

Curator's Choice: A Selection of Instruments from the Museum Stores

Richard Paselk, Curator

Cathetometers

Cathetometers are widely used to measure linear distances accurately and precisely, especially in the vertical direction, and when the apparatus must be observed remotely. They are also used to calibrate the scales on instruments such as mercury barometers, and to read instruments such as liquid column thermometers and manometers to greater precision than the attached scales allow.

The two cathetometers on display came from the Chemistry and Physics deparments. Catalog descriptions are shown below (#19807 and #72730) from two vendors. The vertical cathetometer was one of half-a-dozen or so of these high quality Gaertner Precision cathetometers in the Physics department. The physics department also held a number of lower quality Gaertner cathetometers (#19808 below). The horizontally arrayed Universal cathetometer was used in the Physical Chemistry lab for making precise measurements of the heights of fluid columns in manometers, thermometers etc. It was the top-of-the-line, research grade cathetometer from William Gaertner Corporation, an important maker of research and educational measuring instruments in the laboratory and observatory. Both instruments use verniers, as discussed on the main page for this display, to increase their precision

Gaertner Precision Cathetometer

Catalog scan from: Braun-Knecht-Heiman-Co. (Division of Van Waters & Rogers, Inc.) Catalog No 63, Laboratory Instruments Apparatus and Supplies. San Francisco. (1961) pp 184/5.

Both catalog scans are used with permission from the copyright holders.

Gaertner Universal Cathetometer

Catalog scan from: Cenco. Cat J-300, General Catalog Laboratory Apparatus & Scientific Instruments. Chicago. (c. 1960) p 615.

Cathetometer, Precision

Gaertner Scientific Corp. Chicago

1961; HSU Chemistry Dept. (transferred from HSU Physics)

Designed for high precision vertical measurements. The chrome-plated cold rolled steel scale bar is graduated in 1mm divisions and read to 0.05 mm via a vernier (Gaertner claimed their cathetometers were correct to ±0.010 mm @ 20°C). It is mounted on a tube that may freely rotate on the stand until locked. A 14x telescope with sensitive level, focusing from 29 cm—infinity is mounted with a fine leveling mechanism and vernier scale that slides along the scale bar.

The telescope, level and sliding telescope mount are all painted with a hammertone gray finish.

Height:
Width of base:
Length of Scale: 102.00 cm
Width of cm scale divisions: = 1 cm.
Dimensions of Scale-bar: 47.5" l x 1.25" w x 0.5" thick
Length of telescope including eyepiece and eyepiece extention tube: 10" (open), 7 5/8" (closed). Focusing is via a rack and pinion operated with a black bakelite knob. An anodized aluminum lens cap on a chain protects the objective when not in use.
Length of Level: Level vial housing = 3.5", including mounting tabs = 4.5". The protective vial covering is stamped adjacent to the opening 1 Div.= 30 s, as seen in the close-up image below.

Universal Cathetometer

Gaertner Scientific Corporation, Chicago

Humboldt State College Chemistry Department, 1960

Designed for high precision vertical or horizontal measurements. With its heavy cast iron stand it is displayed mounted horizontally. The German silver scale, graduated in 1mm divisions and read to 0.05 mm via a vernier, is inlet on a heavy square steel bar that turns freely between steel centers on the arms of the stand. As noted in the Cenco catalog description, this instrument was also available with a scale divided to 0.5mm readable to 0.01mm via a vernier with 50 parts (Gaertner claimed their cathetometers were correct to ±0.010 mm @ 20°C).

A 14x telescope (length: 7 3/4) with sensitive level (length: 3 13/16"), focusing from 29 cm—infinity is mounted with a fine leveling mechanism and vernier scale that slides along the scale bar.

The heavy cast iron frame is 52" high (the three leveling screws add from 1.5–2") and 12" wide. The 102 cm scale is engraved on 3/8" wide german silver strip inlaid into a 45 1/4" 2 5/16" x 1 7/8" machined cast-iron bar mounted between hardened steel adjustable pivots allowing 360 rotation with a fine-control clamp at the top (see image below).

The original property decal reads: California State University / Humboldt College / 030199. According to the 1988 HSU inventory it was acquired from Cenco for $1268.80 in 1960.