26 cosmos. 



pendulum has been determined with as much accuracy as the 

 position of the place in respect to its latitude, longitude, and 

 elevation above the level of the sea. 



The pendulum experiments made by the French astrono- 

 mers on the measured part of a meridian arc, and the observ- 

 ations of Captain Kater in the trigonometrical survey of 

 Great Britain, concurred in showing that the results do not 

 individually admit of being referred to a variation of gravity 

 proportional to the square of the sine of the latitude. On 

 this account the English government determined, at the sug- 

 gestion of the Vice-president of the Royal Society, Davies 

 Gilbert, to fit out a scientific expedition, which was intrust- 

 ed to my friend Edward Sabine, who had accompanied Cap- 

 tain Parry on his first polar voyage in the capacity of as- 

 tronomer. In the course of this voyage, which was con- 

 tinued through the years 1822 and 1823, he coasted along 

 the western shores of Africa, from Sierra Leone to the Isl- 

 and of St. Thomas, near the equator, then by Ascension to 

 South America, from Bahia to the mouth of the Orinoco, on 

 his way to the West Indies and the New England States, 

 after which he penetrated into the Arctic regions as far as 

 Spitzbergen, and a hitherto unexplored and ice-bound por- 

 tion of East Greenland (74° 32 7 ). This brilliant and ably- 

 conducted expedition had the advantage of being mainly di- 

 rected to one sole object of investigation, and of embracing 

 points which are separated from one another by 93° of lati- 

 tude. 



The field of observation in the French expedition for the 

 measurements of degrees was more remote from the equinoc- 

 tial and arctic zones ; but it had the great advantage of pre- 

 senting a linear series of points of observation, and of afford- 

 ing direct means of comparison with the partial curvature 

 of the arcs obtained by geodetico-astronomical observations. 

 Biot, in 1824, carried the line of pendulum measurements 

 from Formentera (38° 39' 56 7/ ), where he had already made 

 observations conjointly with Arago and Chaix, as far as 

 Unst, the most northerly of the Shetland Islands (60° 45 / 

 25 /x ), and with Mathieu he extended it to the parallels of 

 Bordeaux, Figeac, and Padua, as far as Fiume.* These 



Croyere), which, however, do not bear comparison with the former in 

 point of accuracy. 



* Biot and Arago, Recueil cTObserv. GeodesiqueS ct Astronomiques, 

 1821, p. 526-540; and Biot, Traite d'Astr. Physique, t. ii., 1811, p. 

 465-173. 



