A VENERABLE CLIMATIC FALLACY 189 



3. The heat energy rendered latent by evaporation is carried 

 across the climatic zone in a relatively ineffective form. — Climate in 

 the common sense of the term relates to the horizon occupied by 

 living things. For convenience in this discussion we may regard 

 the climatic zone as that between the earth's surface and the clouds. 

 The heat energy rendered latent by evaporation crosses this zone 

 embodied in vapor in a non-heating form. It only returns to a 

 heating form when the vapor is condensed into cloud. When 

 condensed into cloud, about half of the heat that returns to the 

 sensible form is radiated outward and is lost; about half is radiated 

 toward the earth and helps to compensate for its previous inertness. 

 But the cloud itself interposes a highly reflective screen between 

 the sun and the earth; a large percentage of the insolation is thus 

 turned back to the sky without passing through the climatic zone 

 or reaching the earth's surface at all. 



There is some compensation, however. The vapor in rising 

 from the surface across the climatic zone is a good absorber and 

 re-radiator, especially of the "dark" rays from the earth. Over 

 the sea this is only brought to bear on the lesser radiation sent 

 forth from the cooler sea surface. On the other hand, the heat 

 sent back from the land crosses the climatic zone more largely in the 

 sensible form and is more largely absorbed in the passage and is 

 repeatedly re-radiated. 



While these considerations are not exhaustive, they sufficiently 

 show that a water surface in high latitude is a cooling agency. 



There is a simple mechanical consideration that deserves passing 

 notice also: 



4, An increase of sea-room in which the warm equatorial currents 

 may spread and cool themselves in intermediate latitudes, reduces their 

 effectiveness in high latitudes. — ^The effectiveness of the oceanic 

 waters in conveying warmth to the polar regions is obviously depend- 

 ent on the conservation of the heat received ia low latitudes, during 

 its long passage to the high latitudes. The more these warmed 

 waters are spread out in their passage from the low to the high 

 latitudes, the earlier will their heat be dissipated and the feebler 

 their effects in the very high latitudes. It is quite clear that if the 

 continents did not concentrate the tropical waters of the Atlantic 



