Description

A fine example and of the very first “compensating” polar planimeter invented and introduced by Gottlied Coradi in 1894.

The present example bears the serial number 1943 both on the label stamped in the cased and one the instrument and is signed by Coradi himself.

“”Gottlieb Coradi (1847–1929) began to make wheel and disc polar planimeters in the early 1880s. In 1894 he made the pole arm higher than the tracer arm and connected the arms with a ball joint. This “compensating” planimeter could trace in both the clockwise and counterclockwise directions, preventing errors introduced by planimeters made in the Amsler style.” (see the Smitsonian for a later example here :https://americanhistory.si.edu/collections/object/nmah_1214984).

The present form is the first type introduced by Coradi and quickly changed in 1895/1896. For the different shape of Coradi polarimeter, see here :

https://www.mathinstruments.ch/en/coradi/gallery.html

The present example is in very fine condition, perfectly preserved, complete with its testing rule.

Everything is preserved in its case measuring 22x8x4,5cm