old philosophers as parts only of the same piece of machinery, we are struck with the fact, and disposed to inquire why is it that the proportion of land and water in the northern hemisphere is very different from the proportion that obtains between them in the southern? In the northern hemisphere, the land and water are nearly equally divided. In the southern, there is several times more water than land. Is there no connection between the machinery of the two hemispheres? Are they not adapted to each other? Or, in studying the physical geography of our planet, shall we regard the two hemispheres as separated from each other by an impassable barrier? Rather let us regard them as made for each other, as adapted to each other, the one as an essential to the other, and both as parts of the same machine. So regarding them, we observe that all the great rivers in the world are in the northern hemisphere, where there is less ocean to supply them. Whence, then, are their resources replenished? Those of the Amazon are, as we have seen (§ 277), supplied with rain from the equatorial calms and trade-winds of the Atlantic. That river runs east, its branches come from the north and south; it is always the rainy season on one side or the other of it; consequently, it is a river without periodic stages of a very marked character. It is always near its high-water mark. For one half of the year its northern tributaries are flooded, and its southern for the other half. It discharges under the line, and as its tributaries come from both hemispheres, it cannot be said to belong exclusively to either. It is supplied with water made of vapour that is taken up from the Atlantic Ocean. Taking the Amazon, therefore, out of the count, the Rio de la Plata is the only great river of the southern hemisphere. There is no large river in New Holland. The South Sea Islands give rise to none, nor is there one in South Africa entitled to be called great that we know of.
290. Arguments furnished by the rivers.—The great rivers of North America and North Africa, and all the rivers of Europe and Asia, lie wholly within the northern hemisphere. How is it, then, considering that the evaporating surface lies mainly in the southern hemisphere—how is it, I say, that we should have the evaporation to take place in one hemisphere and the condensation in the other? The total amount of rain which falls in the northern hemisphere is much greater, meteorologists tell us, than that which falls in the southern. The annual amount of
