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 coulr 
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 ini: 
tude, so that their tendency, if any, must necessarily ‘be to produce 
more than one magnetic pole in.each hemisphere. Thus, ™ 
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 harmon)? 
with the idea of oblique electrical currents; since rotation 1? ‘i 
same direction may be produced by corresponding electro-magnet” 
arrangements. 
