CHAPTER II 

 THE TEMPERATURE OF THE EARTH IN TIME AND SPACE 



The formation of the earth's surface was probably a 

 prelude to the origin of primitive life. The temperature 

 of the earth and its atmosphere has furnished the back- 

 ground which makes the interpretation of heat phenom- 

 ena in animals intelligible. It has also, we believe, fur- 

 nished the stage setting in the story of how some 

 organisms have become homoiothermal. 



The Primitive Earth. — The history of the earth is 

 read in rocks and more recent events are more clearly 

 recorded than those which were more remote. The late 

 history is revealed with great fidelity but the earlier his- 

 tory is indistinct and, if traced back toward its begin- 

 nings, the indistinctness merges into obscurity. Thus 

 the picture of the primitive earth is more a matter of 

 inference than knowledge. 



There have been many attempts to explain the origin 

 of our planet. Astronomers and geologists now gener- 

 ally agree that the solar system was evolved in some 

 way from a nebula of one form or another. The Planet- 

 esimal Hypothesis of Chamberlain (1916) perhaps has 

 the most wide acceptance of any theory of earth origin 

 at present. According to this hypothesis, the original 

 nebula consisted of small bodies, molecules or aggregates, 

 moving in orbits about a common center and forming a 

 disk-like system. The bodies are assumed to have been 

 controlled by revolution about the center of the nebula 



