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 _magnetic longitudinal currents are there_; that they are _lines of force_ and _adequate_; that _oxygen is magnetic_, and therefore the atmosphere must be affected by them--that so far as we can reason from analogy, they ought to produce the effect upon the atmosphere which we find produced, and until further light is thrown upon the subject I shall presume that they do. Every step we take hereafter in this investigation will confirm the presumption. There is one peculiarity to be more particularly noticed before we leave the trade-wind region, and we are now prepared to notice it. The belt of rains, formed by the currents of the two trades, threading their way through each other--how are they produced? Why should the place where the currents thus pass through each other be a place of almost daily precipitation? There is, in fact, no ascension, except that which the currents have in their line of ascent to attain the elevation which the magnetic law of the current requires.