A reprint from American Scientist the magazine of Sigma Xi, The Scientific Research Society This reprint is provided for personal and noncommercial use. For any other use, please send a request to Permissions, American Scientist, P.O. Box 13975, Research Triangle Park, NC, 27709, U.S.A., or by electronic mail to
[email protected]. ©Sigma Xi, The Scientific Research Society and other rightsholders Marginalia Six Months in Ascension J. Donald Fernie early fifty years ago my Venus across the Sun’s face (American Nwife and I joined a handful Thanks in part to Scientist 85:120–122). The tricky part of passengers aboard a freighter out was determining the exact moment the of New York bound for Cape Town, transit began and—hours later—end- South Africa. Our first landfall was a his intrepid wife, ed. Gill was familiar with the meth- small island, only seven or eight miles od, having helped record the transit at its widest, that lies about eight de- David Gill made the of 1874, and had noted several draw- grees south of the equator and half- backs. First, such transits are very rare. way between South America and Af- observations that If something went wrong or clouds rica. The island of Ascension was a interfered it was either 8 or more than welcome sight—but not a pretty one. metered the 19th- 100 years before the next transit. Sec- Even its official Web site describes the ond, to make the estimate as precise island’s surface, covered by old basalt century solar system as possible, teams of observers had to flows and cinder cones, as “rugged, go to widely separated regions across dry, barren, and inhospitable.” the globe.