Sir John Henry Lefroy (28 January 1817 – 11 April 1890) was an English military man and later colonial administrator who also distinguished himself with his scientific studies of the Earth's magnetism. Biography Lefroy was a son of the Rev. John Henry George Lefroy, of Ewshot House (subsequently Itchel) in Hampshire, England, and his wife, Sophia Cottrell. His sister Anne married the Irish landowner and politician John McClintock, who was created the 1st Baron Rathdonnell in 1868. Lefroy was also a first cousin to Thomas Lefroy (1776-1869), the future Chief Justice of Ireland whom Jane Austen apparently had in mind when she created the character of Mr. Darcy in 'Pride and Prejudice'. Lefroy entered the Royal Military Academy, Woolwich in London in 1831 and became a 2nd lieutenant of the Royal Artillery in 1834. When the British government launched a project under the direction of Edward Sabine to study terrestrial magnetism, he was chosen to set up and supervise the observatory on Saint Helena. He embarked on 25 September 1839, for Saint Helena, and carried out his task throughout the following year. In 1842, Lefroy was sent to Toronto as the superintendent of the new Toronto Magnetic and Meteorological Observatory built there as part of that project. He immediately began planning a field expedition to the Canadian northwest to measure magnetism there. With an assistant and a Hudson's Bay Company brigade, he travelled more than 5,000 miles in the Northwest from May 1843 to November 1844, taking measurements at over 300 stations in an attempt to map the geo-magnetic activity of British North America from Montreal to the Arctic Circle, and locate the North Magnetic Pole. They followed the Mackenzie River as far as Fort Good Hope and visited Fort Simpson in the west. On 9 June 1848, Lefroy was made a member of the Royal Society. Lefroy remained in Toronto until 1853, continuing his observations and managing the observatory. On 16 April 1846, he married his first wife Emily Mary, a daughter of Sir John Robinson, 1st Baronet, of Toronto; they had two daughters and two sons. Lefroy also helped found the Royal Canadian Institute, where he was the first vice-president in 1851/52 and then president in 1852/53. Before his return to London, he managed the transfer of the Toronto Magnetic and Meteorological Observatory to the provincial government. Upon his return to London in April 1853, Lefroy held various