Photograph of 1/2 second gravity pendulum apparatus

This photograph shows a 1/2 second gravity pendulum apparatus and camera, which was designed and used by dutch geophysist Prof Meinesz in 1925 as part of his 'Gravtity Expeditions at Sea'. This photograph taken and supplied by the instrument's maker Askania-Werke, which were based in Berlin.

Between 1923 and 1958, Dutch geophyicist and geodesist Professor Meinesz carried out an extensive series of 'Gravity Expeditions at Sea'. Meinesz performed most of these experiments himself onboard Dutch Royal Navy submarines, and using progressively advanced iterations of gravity pendulum apparatus.

This photograph shows one of his earliest designs of gravity pendulums, which was built by German instrument maker Askania. It was likely used on his second expedition in 1926 on a voyage from the Netherlands to Tunis in Tunesia, and later Sabang in Indonesia.

Using gravity pendulums such as this one, Prof Meinesz recorded a vast archive of gravity determinations measured in seas across the globe. He used these measurements to identify variable density of the earth's crust and notably observed many irregular gravitational anomalies along ocean trenches, co-insiding with active volcanism and sharp terrain elevations.

What Prof Meinesz did not entirely realise at the time, was that he had been charting and mapping the fault lines of the Earth's vast tectonic plates, and his work provided some of the foundations for the development of the theory of plate tectonics in the late 1950s.