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

Richard Paselk, Curator

An eclectic collection chosen because of my personal tastes and objects with particular aesthetic appeal expressed to me by non-scientists.

Cool Instruments: Aesthetics, Function and Design in Science

Four items in this eclectic display were chosen because of their particular aesthetic appeal to those outside the sciences. A Southern California contemporary art collector was so taken with the Mettler demonstration balance he requested it for his personal collection. After seeing the Sauter balance displayed in my office, a colleague in Theater Arts returned to take photographs to record its striking design. The clean lines of the centrifuge rotor give it a natural, aerodynamic beauty, though I believe the engineers gave it those lines in part for aesthetic reasons, since its use in a vacuum obviates the need for aerodynamics! And the antique brass microscope represents the classic “brass and glass” scientific objects widely sought for their decorative impact.

Objects are accessed as listed below by shelf from top to bottom and left to right by Case half:

Instrument Vernier Scales for Precision Measurements

Vernier scales allow greater precision for measurements. First publicized by Pierre Vernier in 1631, it became the dominant method for increasing the precision of measuring devices until the late 20^th century advent of modern dial and digital readouts.

In this display vernier scales are seen for the vertical and horizontal divided circles of the universal stage, the Berek compensator, and the petrographic microscope stage. Verniers are also seen for both linear scales on the petrographic microscope mechanical stage and the meter scales on both cathetometers.

In general, as shown in the examples below, the vernier scale improves the precision of the reading by a factor of 10 or more. Note that on the verniers from the cathetometer there are 20 divisions over the same linear distance as 19 mm divisions on the cathetometer scale (each vernier division = 0.95 mm). This difference enables the user to precisely subdivide the mm scale into 0.05 mm subdivisions. Thus on the image below the 0 on the vernier lines up at about 632 mm + 1/3 mm while the 64 cm (640 mm) division aligns exactly with the vernier division at the arrow. The final reading is then 632 mm plus 0.40 mm = 632.40 mm.

• The circle verniers are similar, but the divisions are in degrees. For the image below (the petrographic microscope stage) the 0 on the vernier lines up at about 118° + 1/4° the 120° graduation aligns with the vernier division at the arrow, so the reading is 118° plus 0.2° = 118.2° (or 118° 12’).

© R. Paselk 2013, Last modified 7 February 2021