PORTABLE IRON GAUGER’S ROD, c. early 19th century. Opening on two hinges from 18-5/8″ to 50-1/2″ (47 to 128 cm), the rod has a well-shaped crook-neck handle or belt hanger on one end, and tapered point on the other. One side bears a calibrated linear scale divided every centimeter from 0 to 100, the other a very nonlinear scale again divided every unit from 0 to 100. Here the divisions get closer and closer together proceeding from the bottom; the separation between 0 & 1 is 257 mm, 1 & 2 is 66 mm, and finally 99 & 100 is 4 mm. Condition is fine noting one clip broken.
The rod was probably designed to measure the quantity of liquid in a partially filled vessel of a specific shape. The nonlinear scale suggests volume measurement in a strongly tapered vessel with very narrow base, something like an amphora, and is the first of its kind we have encountered. An interesting project would be to measure all separations, assume a circular cross section, and plot the profile of the intended vessel.
Ask the Dealer
David and Yola Coffeen both have enjoyed academic careers, as planetary astronomer and as linguist/educator. But since 1982 (yes, 1982!) they have been full-time dealers in early scientific and medical instruments, under the name Tesseract. Selling primarily by catalogue (over 100 issued so far) they also have a web presence at www.etesseract.com, and can be contacted at firstname.lastname@example.org.