176 TERRESTRIAL PHENOMENA. 



tension of the atmosphere and the magnetic charge of the 

 Earth. According to Oersted, a conductor is rendered 

 magnetic by the electrical current which passes along it. 

 According to Earaday, magnetism gives rise, by induction, 

 to electrical currents. Thus magnetism is one of the 

 manifold forms under, which electricity shews itself; and 

 the ancient obscure presentiment of the identity of electric 

 and magnetic attraction has been realised in our own 

 days. Pliny, ( 161 ) in accordance with Thales and the Ionic 

 school, says, "The electrum (amber), when animated by 

 friction and warmth, attracts fragments of bark and dry 

 leaves, just as the magnetic stone does iron/' We find a 

 remark to the same effect in a speech of the Chinese philo- 

 sopher Kuopho in praise of the virtues of the magnet. ( 162 ) 

 It was not without surprise that I noticed, on the shores of 

 the Orinoco, children, belonging to tribes in the lowest 

 stage of barbarism, amusing themselves by rubbing the dry, 

 fiat, shining seeds of a leguminous climbing plant (probably 

 a Negretia), for the purpose of causing them to attract 

 fibres of cotton or bamboo. It was a sight well fitted to 

 leave on the mind of a thoughtful spectator a deep and 

 serious impression. How wide is the interval which sepa- 

 rates the simple knowledge of the excitement of electricity 

 by friction, shewn in the sports of these naked copper- 

 coloured children of the forest, from the invention of a 

 metallic conductor which draws the lightning from the 

 storm-cloud, of the voltaic pile effecting chemical decom- 

 position, of a magnetic apparatus evolving light, and of 

 the magnetic telegraph ! Such intervals of separation are 

 equivalent to thousands of years in the progress and intel- 

 lectual development of the human race. 



