172 THE PHYSICAL GEOGRAPHY OF THE SEA. 



Southeast trade-winds the southcast trade-winds, wliicli reach the shores 

 trlceioy^T into rain- of Brazil near the pajallel of Kio, and which blow 

 northeS'hemisphere. thcncc for the most part ovcr the land, should be 

 the winds which, in the general course of circulation, would be 

 carried, after crossing the Andes and rising up in the belt of 

 equatorial calms, toward Northern Africa, Spain, and the South 

 of Europe. They might carry with them the infusoria of Ehren- 

 berg (§ 858), but, according to this theory, they would be want- 

 ing in moisture. Now, are not those portions of the Old World, 

 for the most part dry countries, receiving but a small amount of 

 precipitation? Hence the general rule: those countries to the 

 north of the calms of Cancer, which have large bodies of land 

 situated to the southward and westward of them, in the south- 

 cast trade-wind region of the earth, should have a scanty supply 

 of rain, and vice versa. Let us try this rule : The extra-tropical 

 part of New Holland comprises a portion of land thus situated 

 in the southern hemisphere. Tropical India is to the northward 

 and westward of it ; and tropical India is in the northeast trade- 

 wind region, and should give extra-tropical New Holland a slen- 

 der supply of rain. But what modifications the monsoons of the 

 Indian Ocean may make to this rule, or what effect they may 

 have upon the rains in New Holland, my investigations in that 

 part of the ocean have not been carried far enough for final decis- 

 ion ; though New Holland is a dry country. 



366. The earth is nearer to the sun in the summer of the south- 

 Each hemisphere re- ^^^ hemisphere than it is in the summer of the north- 

 thelameTmlunt"? ^^^ 5 conscqucutly, it has been held that one hemi- 

 ^^**- sphere annually receives more heat than the other. 



But the northern summer is 7.7 days longer than the southern; 

 and Sir John Herschel has shown, and any one who will take the 

 trouble may demonstrate, that the total amount of direct solar 

 heat received annually by each hemisphere is identically the 

 same, and therefore the northern hemisphere in its longer sum- 

 mer makes up with heat for the greater intensity but shorter 

 duration of the southern summer. But though the amount of 

 heat annually impressed by the sun upon each hemisphere be 

 identically the same, it by no means follows that the amount ra- 

 diated off into space by each hemisphere again is also identically 

 the same. There is no reason to believe that the earth is grow- 



