326 



times even of changing the poles. When I de- 

 scribed the magnetic axes of a great mountain 

 of polarized serpentine, situate on the north of 

 Baireuth, in Franconia, Mr. Lichtenberg, the 

 celebrated naturalist of Gottingen, conjectured, 

 that these axes might possibly be the effect of 

 earthquakes, which, in the great catastrophe of 

 our planet, had acted for a long time in the 

 same direction. We know, by the recent ex- 

 periments of Mr. Hauy, that, if heat diminish 

 the magnetic charge, it can also sometimes give 

 certain substances # , in which iron is combined 

 with other principles, the power of being at- 

 tracted by the magnet. We may thereby con- 

 ceive, to a certain point, how earthquakes and 

 volcanic agents, by the changes they produce 

 in the interior of the globe, at great depths, 

 may modify the magnetic phenomena, which 

 we observe at it's surface. I shall not insist on 

 such vague conjectures, but shall confine my- 

 self, to the simple observation, that, at the pe- 

 riods when we felt such violent and frequent 

 shocks in the Cordilleras of Quito, and on the 

 coast of Peru, we were never able to discover 

 any accidental variation in the magnetic dip. 

 It is true, that the analogous changes, produced 

 by the aurora-boreal is in the variation of the 

 needle, like those which I have imagined I re- 



* For example, sulphuretted iron and arseniated pyrites. 



/ 



