346 TERRESTRIAL MAGNETISM. SECT. XXXIV. 



at certain hours of the day the disturbance in the declination 

 may be easterly at Point Barrow, and westerly at the Magnetic 

 Observatory at Toronto, in Upper Canada, and vice versa: in fact, 

 the magnetic storms are simultaneous at these two stations, but 

 in opposite directions a circumstance not yet accounted for, and 

 may possibly be due to the increased magnetism of the air in 

 these cold regions. The heat of the sun has no effect upon 

 terrestrial magnetism unless possibly by its indirect action on the 

 oxygen of the atmosphere; but hitherto it has been impercep- 

 tible. It is hardly possible that the aurora can be independent 

 of the magnetic character of the air, since it occurs in the high 

 latitudes, where the atmospheric magnetism is most powerful. 

 Captain Maguire remarked that it frequently appeared at Point 

 Barrow when the magnetic storms were at a maximum. 



We are totally ignorant of the cause of terrestrial magnetism, 

 though the powerful influence of the solar spots renders it highly 

 probable that it will ultimately be found to originate in the sun 

 himself. Mr. Barlow's theory of electric currents revolving round 

 the globe is borne out by Mr. Fox's observations in the Cornish 

 mines, which show that electro- magnetism is extremely active in 

 metallic veins ; that not only the nature of the metalliferous 

 deposits must have been determined by their relative electrical 

 conditions, but that the direction of the metallic veins must have 

 been influenced by the direction of the magnetic meridians, and 

 in fact almost all the metallic deposits in the world tend from 

 east to west, or from north-east to south-west. However, these 

 currents of electricity may be regarded as magnetic lines of force, 

 and are more likely to be the effect than the cause of terrestrial 

 magnetism. They are found to have a powerful inductive effect 

 on the Atlantic telegraph, disturbing the needles and galvano- 

 meters at each end of the line to a considerable degree, and on 

 the night of the 6th of September, 1858, a magnetic storm passed 

 over the cable, which violently agitated the reflecting galvano- 

 meter in connection with the telegraphic wires. 



We are equally ignorant of the cause of the secular magnetic 

 variations, but we have no reason to believe that the earth is 

 alone magnetic; on the contrary, the planets are probably 

 magnets, and we know that the sun and moon are magnetic ; 

 hence, as the magnetic, like the gravitating force, is transmitted 

 through the ethereal medium, the induction of the sun, moon, 



