Papers of the Board of Longitude : Papers on Edward Sabine's longitude stations

Papers of the Board of Longitude

The observation notebook for longitude readings taken by Captain Edward Sabine at the various stations where he conducted pendulum experiments in his attempt to obtain an accurate account of the figure of the earth. The readings in this volume are dated 1822 and 1823, meaning that Sabine probably carried these observations and calculations with him while he travelled and they were bound later. Between 1821 and 1823 Edward Sabine travelled across most of world with his pendulums and conducted the most extensive collection of measurements that had ever been attempted. The results of this research were published in 1825 at the expense of the Board of Longitude in An account of experiments to determine the figure of the earth by means of the pendulum vibrating seconds indifferent latitude . This work represented the most exhaustive assessment of the figure of the earth, and was also thought by many to be the those most accurate.The data collected in this book is accompanied by an <a href='' onclick='store.loadPage(1);return false;'> introductory letter (RGO 14/50:2)</a> by Sabine explaining that these observations, taken with a reflecting circle by Dollond, were done in order to ascertain the longitude of stations where his pendulum experiments were conducted. This was partially to verify the presumed longitudes for several of these places as well as ensuring that the reduction of his pendulum data would not be effected by an erroneous longitude.This is a book of identical tables all printed out blank; Sabine has filled in the gaps with readings at several field stations whilst the rest of the volume is left full of pages of the <a href='' onclick='store.loadPage(1);return false;'> blank table (RGO 14/50:150)</a>. The page has spaces at the top for observational data and then guides you through the reduction to calculate your longitude and is an interesting example of standardisation in mathematical work in this period.These observations were often taken in the houses of local gentlemen on the various islands that Sabine conducted his pendulum research: The <a href='' onclick='store.loadPage(1);return false;'> observations start (RGO 14/50:3)</a> in Sierra Leone at the West Bastion of Fort Thornton on Feb 28th and the <a href='' onclick='store.loadPage(1);return false;'> last page (RGO 14/50:20)</a> is dated the April 2nd 1822. Sabine then moves over to the Island of St Thomas with the <a href='' onclick='store.loadPage(1);return false;'> first reading (RGO 14/50:26)</a> taken on May 29th 1822 in the mansion house at Man of War Bay. On the 26th of June 1822 the <a href='' onclick='store.loadPage(1);return false;'> first data (RGO 14/50:37)</a> from Ascension Island was collected and Sabine remains there in the Barrack Square, “at the foot of Cross Hill” till July 3rd. The next <a href='' onclick='store.loadPage(1);return false;'> entry (RGO 14/50:53)</a> in the volume comes on July 25th after Sabine has journeyed to Bahia, where he stayed in the house of William Pennell to conduct his pendulum experiments, with the <a href='' onclick='store.loadPage(1);return false;'> last longitude calculation (RGO 14/50:66)</a> on that island dated the 31st July 1822. At the end of August we see <a href='' onclick='store.loadPage(1);return false;'> longitude calculations (RGO 14/50:67)</a> for Maranham, where Sabine stayed in the house of Robert Hesketh. A month later on the 23rd of September there are <a href='' onclick='store.loadPage(1);return false;'> longitude calculations (RGO 14/50:83)</a> for Trinidad where Sabine stays “in the second Ground-lot, West of the Protestant Church, Port Spain” and then finally at the end of October, on the 23rd Sabine stayed at Port Royal in Jamaica and conducted <a href='' onclick='store.loadPage(1);return false;'> longitude calculations (RGO 14/50:99)</a> till the 5th of November.Also in the volume are several additional notes and readings, for example a <a href='' onclick='store.loadPage(1);return false;'> note (RGO 14/50:105)</a> written from Spitsbergen where Sabine observed transits of the moon with Mr Henry Foster which reads: “The end of the solar eclipse which happened on the 8th of July was observed at the same spot by Mr Henry Foster and Myself.” Foster used an achromatic telescope made by Dolland and Sabine noted that “Mr Foster's observation is truthful to the mean, on account of the superiority of his telescope”, further its recorded that they used government owned chronometers, no. 649 and 423.Sophie Waring History and Philosophy of Science University of Cambridge