SIR EDWARD SABINE. 561 



age, to the credit of which his individual hibors have so essentially 

 contributed." The intensity of the magnetic force of the earth, the 

 dip and declination of the magnetic needle, and the irregularities in 

 its action produced by tlie iron in the ship, especially in latitudes 

 where the directive force of the earth is feeble, were conspicuous 

 among the subjects which interested Sabine and were discussed in his 

 earlier publications. 



The exact figure of the earth may be studied in three ways: 1. by 

 inequalities in the moon's motion; 2. by measuring the lengths of a 

 degree of the meridian in different latitudes ; and 3. by the compara- 

 tive values of the force of gravity in various places, as indicated by the 

 pendulum. In the years 1821-23, Sabine, adopting the last method, 

 vibrated his pendulum at numerous places between the equator 

 and Spitzbergen, and the results of his experiments, spread over 

 eighty degrees of latitude, were published, in 1825, in a thick quarto 

 volume, by the Board of Longitude. For this laborious and able in- 

 vestigation Sabine received the Lalaude Gold Medal from the lustitut 

 de France. Biot and Babbage have criticised this work ; but the 

 numerical value which Sabine assigned to the ellipticity of the earth 

 is substantially sustained by all the experiments with the pendulum to 

 the present time. In 1825 Captain Sabine and Sir John Herschel 

 were appointed Commissioners to cooperate with a French Commis- 

 sion in order to ascertain the difference of longitude between the obser- 

 vatories of Greenwich and Paris, by means of optical signals. The 

 value then obtained differs by only six tenths of a second of time from 

 that now given by electric signals. In 1828, Sabine, Young, and 

 Faraday were appointed " scientific advisers of the Admiralty," 



The last forty-six years of Sabine's scientific activity were dedicated 

 to the study of terrestrial magnetism. In 1834-37, he made, in 

 conjunction with Rev. Ilumjjhrey Lloyd, or Captain J. C. Ross, a 

 systematic magnetic survey of Ireland, Scotland, and England. The 

 observations, the I'eductions, and the reports on the subject, published, 

 with maps, by the British Association, were to a large extent his own 

 work. In 1858-61, at the request of the British Association, he 

 repeated the survey, with the assistance of Di-. Lloyd ; and with the aid 

 of Captain Evans calculated and reported the values of the dip, decli- 

 nation, and intensity. In his first Arctic voyage, Sabine had noticed 

 with surprise that the magnetic intensity was diminishing in Baffin's Bay 

 while he was moving northward. Hence he suspected that the pole of 

 magnetic intensity was south of his position : a suspicion which was 

 justified by observations made in New York in 1822, where the inten- 



VOL. XIX. (n. S. XI.) 30 



