Where did Life Begin f 13 



heat received by the earth being infinitesimal 

 in comparison, is not here taken into the cal- 

 culation. But were it more considerable, it 

 would not be important in this connection, for 

 it falls upon all parts of the earth about equally. 



It is evident from the present condition of 

 the earth's surface, that at the time it was a 

 molten mass, and for a long time thereafter, it 

 radiated heat into space much more rapidly 

 than it received heat from the sun ; but never- 

 theless the heat of the sun is, and always has 

 been, offsetting the loss of heat from the earth 

 by radiation to the full extent of the heat 

 which the earth had been receiving from the 

 sun during the time. 



But this sun-heat, this offset to radiation, 

 has not been received by all parts of the earth 

 equally. The equatorial belt, or torrid zone, 

 has always received the most per square foot, 

 or in proportion to fts area. The two inter- 

 mediate or temperate zones have received 

 the next largest amount per square foot, or in 

 proportion to their area ; while the polar or 

 frigid zones have received the least per 

 square foot, or in proportion to their area. 



