RAINS AND RIVERS. 117 



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 diiferent 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 ? Eather 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. ^Vhence, 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 Eio 

 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 hy the rivers. — The great rivers of 

 North America and North Africa, and all the rivers of Europe 

 cind 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 conden- 

 sation 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 



