The 1874 Transit of Venus Expedition to Hawaii was an astronomical expedition by British scientists to observe the December 8 transit of Venus at three separate observing sites in the Hawaiian Islands, then known as the Sandwich Islands. It was one of five 1874 transit expeditions organized by George Biddell Airy, Astronomer Royal at the Royal Observatory, Greenwich. The purpose of the expedition was to obtain an accurate estimate of the astronomical unit (AU), the distance from the Earth to the Sun, by measuring solar parallax. Previous efforts to obtain a precise value of an AU in 1769 had been hampered by the black drop effect. There is a collection of papers relating to this expedition at the Cambridge Digital Library.