THE PHYSICAL GEOGEAPHY OF THE SEA. 



1.291 oz., and its specific gravity .00129. Such is the diiference 

 in weight between the two elements, the phenomena of which 

 give the physical geography of the sea its charms as a study. 



19. There is in the northern hemisphere more land, less sea, 

 Unequal distribution "i^re frcsh watcr, and more atmospheric air, than 

 of light, etc. there is in the southern. 



20. The sun dispenses light and heat unequally also between 

 The sun longer in them. lu his auuual round he tarries a week (7|- 

 tiun. days) longer on the north than he does on the south 

 side of the equator, and consequently the antarctic night and its 

 winter are both longer, and should, if there were no interferences, 

 be more intense than the polar winter and jiight of the arctic re- 

 gions. The southern hemisphere is said also to be cooler, and 

 this is true to a certain degree. In the summer of the southern 

 hemisphere the sun is in perigee, and during the course of a di- 

 urnal revolution there the southern half of our planet receives 

 more heat than the northern half during the same period of our 

 summer. This difference. Sir John Herschel thinks, is compen- 

 sated by the longer duration of the northern summer. Admit- 

 ting this to be so — and it is susceptible of mathematical demon- 

 stration — there remains outstanding the longer winter for the 

 southern hemisphere, which may radiate more heat than the 

 northern hemisphere can do in its short winter. But the south- 

 ern hemisphere is the cooler chiefly on account of the latent heat 

 w^hich is brought thence by vapor, and set free here by conden- 

 sation. 



21. Within the torrid zone the land is nearly equally divided 

 England about the uorth and south of the equator, the proportion be- 



pole of hemisphere ..-.-ri t t 



xrith most land. lug as o to 4. lu the tcmpcratc zones, however, the 

 north with its land is thirteen times in excess of the south. In- 

 deed, such is the inequality in the distribution of land over the 

 surface of the globe that the world may be divided into hemi- 

 spheres consisting, the one with almost all the land in it, except 

 Australia and a slip of America lying south of a line drawn from 

 the Desert of Atacama to Uruguay ; England is the centre of this 

 hemisphere. The other, an aqueous hemisphere, contains all the 

 great waters except the Atlantic Ocean; New Zealand is the 

 nearest land to its centre. 



22. Tliis unequal distribution of land, air, and water is suggest- 



