66 COSMOS. 



Bay Company, 1838-1839 ; and more recently, in search of 

 Sir John Franklin, the expeditions of Captains Ommanney, 

 Austin, Penny, Sir John Ross, and Phillips, 1850 and 1851. 

 r jDhe expedition of Captain Penny reached the northern lat- 

 itude of 77 6' Victoria Channel, into which Wellington 

 Channel opens. 



1819-1821. Bellinghausen's Voyage into the Antarctic 

 Ocean. 



1819. The appearance of the great work of Hansteen On 

 the Magnetism of the JSa^th, which, however, was completed 

 as early as 1813. This work has exercised an undoubted 

 influence on the encouragement and better direction of geo- 

 magnetic studies, and it was followed by the author's gener- 

 al charts of the curves of equal inclination and intensity for 

 a considerable part of the earth's surface. 



1819. The observations of Admirals Roussin and Givry 

 on the Brazilian coasts, between the mouths of the rivers 

 Maranon and La Plata. 



1819-1820. Oersted made the great discovery of the fact 

 that a conductor that is being traversed by a closed electric 

 current exerts a definite action upon the direction of the 

 magnetic needle according to their relative positions, and as 

 long as the current continues uninterrupted. The earliest 

 extension of this discovery (together with that of the ex- 

 hibition of metals from the alkalies and that of the two 

 kinds of polarization of light probably the most brilliant 

 discovery of the century)* was due to Arago's observation, 

 that a wire through which an electrical current is passing, 

 even when made of copper or platinum, attracts and holds 

 fast iron filings like a magnet, and that needles introduced 

 into the interior of a galvanic helix become alternately 

 charged by the opposite magnetic poles in accordance with 

 the reversed direction of the coils (Ann. de Chim. et de Phys., 

 t. xv., p. 93). The discovery of these phenomena, which 

 were exhibited under the most varied modifications, was fol- 

 lowed by Ampere's ingenious theoretical combinations re- 

 garding the alternating electro-magnetic actions of the mole- 

 cules of ponderable bodies. These combinations were con- 

 firmed by a series of new and highly ingenious instruments, 

 and led to a knowledge of the laws of many hitherto appar- 

 ently contradictory phenomena of magnetism. 



1820-1824. Ferdinand von WrangePs and Anjou's expe- 



* Malus's (1808) and Arago's (1811) ordinary and chromatic polari- 

 zation of Light. See Cosmos, vol. ii., p. 332. 



