420 



Gilpin and of Beaufoy, omitting however to mention the important 

 ones by Canton, he observes that the arctic expeditions have fur- 

 nished a rich harvest of important observations to Captains Sabine* 

 Franklin, Parry, Foster, Beechey, and James Ross, and Lieutenant 

 Hood*- and that thus physical geography is indebted to the at- 

 tempts which have been made to discover the north-west passage, 

 and also to the explorations of the icy coast of Asia, by Wrangel, 

 Lutke, and Anjou, for a considerable accession of knowledge in ter- 

 restrial magnetism and meteorology. Excited, he observes, by the 

 great discoveries of Oersted, Arago, i\mpere, Seebeck, and Faraday, 

 MM. Hansteen, Due and Adolphe Erman have explored, in the 

 whole of the immense extent of Northern Asia, the course of the iso- 

 clinal, isogonal, and isodynamic curves ; and M. Adolphe Erman has 

 had the advantage during a long voyage from Kamtschatka round 

 Cape Horn to Europe, of observing the three manifestations of ter- 

 restrial magnetism on the surface of the earth, with the same in- 

 struments and by the same methods which he had employed from 

 Berlin to the mouth of the Obi, and thence to the sea of Okhotsk. 



M. de Humboldt remarks that our epoch, marked by great disco- 

 veries in optics, electricity, and magnetism, is characterized by the 

 possibility of connecting phenomena by the generalization of em- 

 pirical laws, and by the mutual assistance rendered by sciences 

 which had long remained isolated. Now, he observes, simple ob- 

 servations of horary variation or of magnetic intensity made at 

 places far distant from each other, reveal to us what passes at great 

 depths in the interior of our planet or in the upper regions of our 

 atmosphere : those luminous emanations, those polar explosions 

 which accompany the " magnetic storm" appear to succeed the 

 changes which the mean or ordinary tension of terrestrial magnetism 

 undergoes. 



M. de Humboldt considers that it deeply interests the advance- 

 ment of mathematical and physical sciences that, under the auspices 

 of His Royal Highness the President, the Royal Society should 

 exert its influence in extending the line of simultaneous observa- 

 tions, and in establishing permanent magnetic stations in the tro- 

 pical regions on both sides of the magnetic equator, in high south- 

 ern latitudes, and in Canada. He proposes this last station because 

 the observations of horary variation in the vast extent of the United 

 States are yet extremely rare. Those at Salem, calculated by Mr. 

 Bowditch, and compared by Arago with the observations of Cassini, 

 Gilpin, and Beaufoy, may, he remarks, guide the observers in Canada, 

 in examining whether there, contrary to what takes place in Western 

 Europe, the (diurnal ?) variation does not decrease in the interval 

 between the vernal equinox and the summer solstice. 



In a memoir published five years ago, M. de Humboldt states that 

 he has indicated as stations extremely favourable for the advance- 

 ment of our knowledge, New Holland, Ceylon, the Mauritius, the 



* To this long list we may now add the name of Captain Back; nor ought 

 the name of Mr. Fisher to be omitted. 



