142 Electro-magnetic properties of the mines of Cornwall. 



has been noticed by Baron Humboldt, that the stratification of primi- 

 tive rocks in different and far distant parts of the world, has a general 

 tendency from the north east towards the south west. 



Such analogies become highly interesting when regarded in con- 

 nection with terrestrial electricity, magnetism and heat ; for if it be 

 granted that the two latter increase in intensity at great depths in the 

 earth, they are evidently so connected with electrical action that the 

 augmentation of it also, in the interior of the globe, may be reason- 

 ably inferred. 



However this may be, assuming that metalliferous veins exist more 

 or less in primitive rocks generally, and experience favors this as- 

 sumption, whether we refer to the new mines which have been dis- 

 covered in various parts of North and South America, Siberia, Ire- 

 land, &.C. or to the mining county of Cornwall, in which whole dis- 

 tricts have comparatively of late been found abounding with mineral 

 treasure, where none have been formerly supposed to exist, it may 

 be presumed, that the electrical currents, which so affect the needle 

 in the galvanometer, may likewise influence the direction of the mag- 

 netic needle on the surface of the earth ; at least no explanation of 

 this phenomenon appears to be so plausible or so well connected with 

 ascertained facts. Even the cause of the variations of the needle, 

 mysterious as it has hitherto appeared to be, may probably be refer- 

 red to the relative energies of the opposing electrical currents, which 

 are perhaps subject to occasional modifications; and the appearance 

 of earthquakes and volcanic action, from time to time, seems to coun- 

 tenance the probability of such changes. 



Nor should it be overlooked, in reference to this view of the sub- 

 ject, that the oblique bearing which is generally observable in the 

 strata and veins, with respect to the equator, causes them, as it were, 

 to cross at opposite sides of the globe, in the same parallels of lati- 

 tude, so that their tendency, if any, must necessarily be to produce 

 more than one magnetic pole in each hemisphere. Thus, in this 

 respect also, the hypothesis accords with the interesting fact lately 

 announced ; — of Professor Hansteen having ascertained the exist- 

 ence of a second magnetic pole within the arctic circle. The revo- 

 lution of the earth on its axis from west to east, seems to harmonize 

 with the idea of oblique electrical currents ; since rotation in the 

 same direction may be produced by corresponding electro-magnetic 

 arrrangements. 



