4-8 Baron Humboldt o« advaticing the Kno-doledge 



have found these periods too near to each other, it has been 

 thought advisable to insist in preference upon the time of the 

 solstices and equinoxes. 



England, from the time of William Gilbert, Graham, and 

 Halley to that of the more recent exertions of Messrs. Gilpin, 

 Beauiby (at Bushy), Barlow, and Christie, has produced a 

 rich collection of materials applicable to the discovery of the 

 physical laws which regulate the variation of the magnetic de- 

 clination, either in one place according to the different hours 

 and seasons, or at various distances from the magnetic equator 

 and the lines without declination. Mr.Gilpin made observations 

 during twelve hours every day for more than seven months. 

 The numerous observations of Colonel Beaufoy were regularly 

 published in Thomson's Annals. The memorable expedi- 

 tions to the most inhospitable regions of the North have fur- 

 nished Messrs. Sabine, Franklin, Hood, Parry, Henry Foster, 

 Beechey, and James Clarke Ross with a rich harvest of im- 

 portant observations. Physical geography is indebted for a 

 considerable increase of knowledge respecting terrestrial mag- 

 netism and meteorology to the attempts which have recently 

 been made to determine the form of the north-west passage 

 or strait; and to the perilous explorations of the frozen coasts 

 of Asia by Captains Wrangel, LUtke, and Anjou. During the 

 progress of these noble efforts, an unexpected impulse has 

 been given to the physical sciences by the light thrown upon 

 them by a branch of natural philosophy the theoretical pro- 

 gress of which for two centuries had been extremely slow. 

 Such has been the effect of the grand discoveries of Oersted, 

 Arago, Ampere, Seebeck, and Faraday upon the nature of 

 electro-magnetic forces. Excited by the talents and ingenious 

 exertions of learned travellers cooperating for the promotion 

 of one object, Messrs. Hansteen, Due, and Adolphus Erman, 

 by the fortunate union of very precise astronomical and phy- 

 sical means, have explored, throughout the immense extent 

 of Northern Asia, the isoclinal, isogonal, and isodynamic 

 curves for very nearly the same epoch. When speaking of 

 this great project, long since conceived and proposed by Mr. 

 Hansteen, I ought, perhaps, to pass over in silence the obser- 

 vations upon magnetic inclination which I made upon the 

 rarely-visited frontier of Chinese Dzoungarie and on the 

 coasts of the Caspian Sea, published in the second vo- 

 lume of my Fragmetis Asiatiques. My learned countryman 

 Mr. Adolphus Erman, who embarked at Kamtschatka and re- 

 turned to Europe by Cape Horn, had the rare advantage of 

 continuing throughout a long voyage the measure of the three 

 manifestations of terrestrial magnetism at the surface of the 



