| |

Deutsches Technikmuseum - May

Site Navigation Menus


website overview

The Websites of the donation Stiftung Deutsches Technikmuseum Berlin at a glance:

Stiftung

The donation contains six locations:

Exhibit of the Month May 2011

Photo: A bulbous light blue coffee pot, made from porcelain, designed in the twenties. The spout is broken.

Worldwide one of the oldest Jacob´s Staffs © C. Kirchner/SDTB

Jacob’s Staff, around 1700, probably from southern Germany

What is it? What was the function of the 50-centimetre-long, wooden rod with ivory overlays?

For decades it was in the cabinet of M. Gräfe’s grandmother and the family believed it to be a tailor’s measuring stick. The lender set out to solve the riddle and found a surprise: it is the vertical rod of a Jacob’s Staff, which is used for surveying. The cross bar has not survived.

Nearly 130 Jacob’s Staffs are known worldwide, most dating from the 18th century. This one is estimated to be older. Its ivory design is unusually sophisticated; the scale and labeling are precise and handmade.

A measuring tool for astronomy and surveying

A Jacob’s Staff is a protractor, which measures the angle between two points. Such points can be mountain peaks, landscape or buildings, stars or the horizon. This measuring tool for astronomy and surveying was first described by the Greek mathematician Archimedes (300 B.C.) and introduced in Western Europe in the 14th century.

The name "Jacob’s Staff” is traced back to the similarity of the instrument to a constellation, which at that time was compared with the pilgrim’s staff of Jacobus Major—the Holy Jacob, a disciple of Jesus. From the 16th to the middle of the 18th centuries, the Jacob’s Staff also gained acceptance in European seafaring as a method for determining latitude. Then it lost its significance.