J. S. T. Gehler (1751–1795), a private lecturer of mathematics who lived in Leipzig, went down in the history of science mainly due to his work entitled ‹Physikalisches Wörterbuch‹ (Physical Dictionary). This work, which even the famous contemporary physicist Lichtenberg described as »excellent,« is still being used regularly by historians of science today. The two volumes published reflect the state of knowledge in physics towards the end of the 18th century.