112 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. 



■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 yery 

 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 ? Ai'e 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 

 l)arrier ? Eather let us regard them as made for each other, as 

 adapted to each other, the one as an essential to the other, and 

 Loth 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 som^ces 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 ^vithout 

 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 fi^om 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 Afiica entitled to be called great that we know of. 

 290. The great rivers of North America and North Africa, and 

 Arguments furnished all tlic rivors of Em'opo and Asia, lie wholly ■within 

 y I e nvere. ^-j^^ northom hemisphere. How is it, then, consider- 



ing that the evaporating sm-face lies mainly in the southern hemi- 

 sphere — 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 fall^ in the northern hemisphere 

 is much greater, meteorologists tell us, than that which falls in the 

 southern. The annual amount of rain in the north temperate 

 zone is half as much again as that of the south temperate. How 

 is it, then, that this vapour gets, as stated, from the southern into 

 the northern hemisphere, and comes mth. such regularity that our 



