Six Months in Ascension, first published in 1878, contains an account by Isobel Sarah B. Gill of the 1877 scientific expedition to the island of Ascension, in the South Atlantic, undertaken to measure the distance of the sun from the earth by observing the opposition of the planet Mars. The expedition, funded by the Royal Astronomical Society, was led by Isobel's husband, the astronomer David Gill, with a heliometer and other scientific instruments provided by Lord Lindsay. Isobel accompanied the expedition as her husband's companion. Her account offers personal details and stories omitted from the scientific reports on the expedition written by her husband and colleagues and it contains beautiful descriptions of the island of Ascension. The book offers a rare view of the personal, practical and behind-the-scenes side of a nineteenth-century scientific expedition and provides a fascinating insight into the gender roles of learned Victorian society.