filings will
not adhere_ to any considerable extent. The lines shown upon the needle
should bear the same proportion to its length as the trade-winds bear to
that of the earth, measured from pole to pole, and if the needle had a
globular form they would so appear.

These lines are made by currents arising from one side of the magnetic
equator, and passing over to the other. Doubtless, just such currents
rise, and pass over upon the earth.

Magnetic and electric currents carry the air with them. This is well
settled by experiment. _Oxygen_, too, is _magnetic_, and capable both of
receiving and retaining polarity and of combining with, or attracting and
retaining vapor, and of course the moisture of evaporation. Here then we
have a power existing, capable of producing the result--precisely, and
with evident wisdom adapted to its production--ever present and active;
and no other known agent can.

Is it not then the agent?

Let us look a little further. This result is affected by the action of the
sun: the trades with the central belts of rains travel north and south
after it; so does the sun affect the magnetic currents every where, even
the magnetic needle is daily affected by its action, as it increases the
intensity of the terrestrial magnetic currents, and hence its well
established diurnal oscillations.

Again, along the eastern lines of the continents which skirt the great
oceans on the west, run the northerly and southerly lines of no variation,
and of greatest magnetic intensity. Here are the trade currents gathered
into a volume, which curve and carry unusual fertility to South-eastern
Asia, and North America, and in those great aerial gulf streams we find
the _intense_ electric action which produces the typhoons of the former,
and the hurricanes of the latter. It may still be said that these
conditions and phenomena of the trade-wind region, are not produced by
magnetism or magneto-electricity, _but the objector can point to no other
adequate power_. That it must be heat, electricity, or magnetism, must be
admitted. There is no other power known. Heat demonstrably can not produce
them. Magnetism or electricity therefore must, and they are doubtless
states or phases of the same power, producing in their different states or
phases the different results. And even heat--atmospheric temperature, is
often, if not always the result of their action. In the present state of
science, it is enough for me that the _magn