MAGNETISM. 



tonishraent, on the wojdy banks of the Orinoco, in the sports 

 of the natives, that the excitement of electricity by friction 

 was known to these savage races, who occupy the very lowest 

 place in the scale of humanity. Children may be seen to rub 

 the dry, flat, and shining seeds or husks of a trailing plant 

 (probably a Negretia) until they are able to attract threads 

 of cotton and pieces of bamboo cane. That which thus de- 

 lights the naked copper-colored Indian is calculated to awaken 

 in our minds a deep and earnest impression. What a chasm 

 divides the electric pastime of these savages from the discov- 

 ery of a metallic conductor discharging its electric shocks, or a 

 pile composed of many chemically-decomposing substances, or 

 a light-engendering magnetic apparatus ! In such a chasm 

 lie buried thousands of years that compose the history of the 

 intellectual development of mankind ! 



The incessant change or oscillatory motion which we dis- 

 cover in all magnetic phenomena, whether in those of the in- 

 clination, declination, and intensity of these forces, according 

 to the hours of the day and the night, and the seasons and the 

 course of the whole year, leads us to conjecture the existence 

 of very various and partial systems of electric currents on the 

 surface of the Earth. Are these currents, as in Seebeck's ex- 

 periments, thermo-magnetic, and excited directly from unequal 

 distribution of heat ? or should we not rather regard them as 

 induced by the position of the Sun and by solar heat ?* Have 

 the rotation of the planets, and the different degrees of velocity 

 which the individual zones acquire, according to their respect- 

 ive distances from the equator, any influence on the distribu 

 tion of magnetism ? Must we seek the seat of these currents, 

 that is to say, of the disturbed electricity, in the atmosphere, 

 in the regions of planetary space, or in the polarity of the Sun 

 and Moon ? Galileo, in his celebrated Dialogo, was inclined 

 to ascribe the parallel direction of the axis of the Earth to a 

 magnetic point of attraction seated in universal space. 



If we represent to ourselves the interior of the Earth as 

 fused and undergoing an enormous pressure, and at a degree 

 of temperature the amount of which we are unable to assign, 



* " The phenomena of periodical variations depend manifestly on the 

 action of solar heat, operating probably through the medium of thermo- 

 electric currents induced on the Earth's surface. Beyond this ruda 

 guess, however, nothing is as yet known of their physical cause. It is 

 even still a matter of speculation whether the solar influence be a prin- 

 cipal or only a subordinate cause in the phenomena of terrestrial mag- 

 netism." (Observations to be made in the Antarctic Exrtdifion, 18-10 

 I' -31.) 



