'Eclipses' and 'The Theory of the Tides', c 1860.
© Science Museum / Science & Society Picture Library
One of a set of teaching cards published by James Reynolds & Sons, London, England around 1860. Titled 'Eclipses & The Theory of the Tides', the chart was drawn and engraved by John Emslie. The uppermost astronomical diagram shows how the Earth and Moon can cast shadows on each other to cause lunar and solar eclipses. The lower diagram in contrast shows how the position of the Moon with respect to the Sun and Earth controls the timing and the magnitude of the tides in our oceans. The left figure shows how Neap (lower) High Tides occur, while the right one illustrates the cause of Spring High Tides (higher).