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Events on Saturday 13 September 1845 2
1845Faraday effect discoveredMagnetism shown to affect lightMichael Faraday found that a magnetic field rotates the plane of polarised light passing through glass. It was the first experimental evidence of a link between light and electromagnetism. The discovery helped lay the ground for Maxwell's electromagnetic theory of light.
1845Potato blight reaches IrelandStart of the Great FamineThe water mould Phytophthora infestans destroyed much of Ireland's potato crop in the autumn of 1845, after appearing in continental Europe that summer. Most of the Irish rural poor depended on the potato for food. The failures that followed caused about a million deaths and drove more than a million people to emigrate over the next several years.