On the anniversary of the discovery of logarithms 400 years ago, the Arithmeum in Bonn presents a selection of the collection by Ijzebrand Schuitemas (1929-2013), which contains more than 4,000 slide rules. The exhibition catalogue introduces the brilliant idea of the slide rule, shows its interesting history and deals with the diversity of this calculating instrument, which became indispensable for numerous professional groups and which were still used in various ways until well into the 20th century. The introduction of the calculator meant the demise of this historically and culturally fascinating object.