'The Seasons and Signs of the Zodiac', 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 'The Seasons', the chart was drawn and engraved by John Emslie. The diagram shows how the Earth's axis of rotation is tilted with respect its path around the Sun, but its direction in space is fixed. As the Earth moves along its orbit during the course of the year, the Sun's height in the sky varies along with the length of the day. In temperate latitudes this causes the seasons that alternate between the Northern and Southern Hemispheres.