64 COSMOS. 



the magnetic and astronomical portion was by Horner (bd. 

 iii., s. 317). 



1804. Investigation of the law of the increase in the in- 

 tensity of terrestrial magnetic force from the magnetic equa- 

 tor northward and southward, based upon observations made 

 from 1799 to 1804. (Humboldt, Voyage aux Regions Equi- 

 noxiales du Nouveau Continent, t. iii., p. 615-623 ; Lametherie, 

 Journal de Physique, t. Ixix., 1804, p. 433 ; the first sketch 

 of a chart showing the intensities of the force, Cosmos, vol. i., 

 p. 185.) Later observations have shown that the minimum 

 of the intensity does not correspond to the magnetic equator, 

 and that the increase of the intensity in both hemispheres 

 does not extend to the magnetic pole. 



1805-1806. Gay-Lussac and Humboldt, Observations of 

 Intensity in the south of France, Italy, Switzerland, and 

 Germany. Memoires de la Societe d'Arcueil, t. i., p. 1-22. 

 Compare the observations of Quetelet, 1830 and 1839, with 

 a *' Carte de I'intensite magnetique horizontale entre Paris 

 et Naples," in the Mem. de'VAcad. de Bruxelles, t. xiv. ; the 

 observations of Forbes in Germany, Flanders, and Italy, in 

 1832 and 1837 {Transact, of the Royal Soc of Edinburgh, \o\. 

 XV., p. 27); the extremely accurate observations of Eiidberg 

 in France, Germany, and Sweden, 1832 ; the observations 

 of Dr. Bache (Director of the Coast Survey of the United 

 States), 1837 and 1840, at twenty-one stations, both in refer- 

 ence to inclination and intensity. 



1806-1807. A long series of observations at Berlin on 

 the horary variations of declination and the recurrence of 

 magnetic storms (perturbations), by Humboldt and Oltmanns, 

 mainly at the periods of the solstices and equinoxes for five 

 and six, or even sometimes nine days, and as many nights 

 consecutively, by means of Prony's magnetic telescope, which 

 allowed arcs of seven or eight seconds to be distinguished. 



1812. Morichini, of Rome, maintained that non-magnetic 

 steel-needles become magnetic by contact with the violet rays 

 of light. Regarding the long contention excited by this as- 

 sertion, and the ingenious experiments of Mrs. Somerville, 

 together with the wholly negative results of Riess and Moser, 

 see Sir David Brewster, Treatise on Magnetism, 1837, p. 48. 



1815-1818.") ^, , . . ,. r.^,, 



^ono_i oop f The two circumnavigation voyages ot Otto 



von Kotzebue : the first in the Ruric ; the second, five years 

 later, in the Predprijatie. 



1817-1848. The series of great scientific n/aritime expe- 



