Friedrich Robert Helmert died in Potsdam in 1917. He was, for over 30 years, director of the Royal Prussian Geodetic Institute and of the Central Bureau of the Internationale Erdmessung, today's IAG. He dedicated his life and his scientific career to the field of geodesy. His teachings on theoretical and physical geodesy were incorporated into university curricula around the world and hence into international endeavours to measure planet Earth. Hide

Historical geographical works typically contain many latitude measurements of locations: all show measurement errors and some of these refer to lost cities. How can we estimate errors? How can we know the right position of lost cities? This work shows a general approach to give a scientific answer to these questions in two particular case studies: Ptolemy's Geography and Riccioli's work on geography. Hide

This article presents the most important facts on the life and scientific achievements of Steponas Kolupaila (1892–1964) – one of the most famous hydrologists of the 20th century. This Lithuanian scientist is especially well known for his book Bibliography of Hydrometry. Hide

An analysis is given of the account of a globe of fire observed in Zafra (Spain) in the middle of the 16th century. During a strong storm, Conde Don Pedro observed what he described as a globe of fire that was directed against the city and abruptly changed course. He attributed the change in course to a miracle. He described neither any damage nor sound. Hide