62 INTRODUCTION TO GENERAL SCIENCE 



Lockyer and Darwin modified this theory by considering 

 that the material originally was in the form of cold meteors. 

 These, on account of the distance between the separate 

 meteors, would act like a gas, and the heat could have been 

 produced by the collision and compression of a large number 

 of these meteors. Thus there was no necessity for original 

 heat. This theory has been given the name Meteoritic Hy- 

 pothesis. 



Lastly, a modification of the La Place Hypothesis states 

 that the material was not in equilibrium at the beginning, but 

 whirling in a vast spiral, the different parts of the spiral break- 

 ing up to form the Solar System. This is called the Spiral 

 Nebular Hypothesis. 



Since we are considering the beginning of things, a defini- 

 tion of the word evolution might not be out of place. By 

 evolution is meant the slow change from the simple and un- 

 organized to the complex and highly organized. Such a 

 change usually takes a very long period of time, which cannot 

 be reckoned in years, but in millions of years. 



References : 



1. 1002 : 446-449. La Place Ring Hypothesis. 



2. 1002 : 448. Meteoritic Hypothesis. 



3. 1002 : 453-458. La Place Ring Hypothesis. 



4. 1002 : 463-466. Spiral Nebular Hypothesis. 



5. 1002 : 485-487. The Past and Future of the Solar System, 



6. 1205 : 304-305. The Earth's Beginnings. 



a. 1001 : 353-356. Genesis and Nebular Hypothesis. 



6. 1003 : 224. The Nebular Hypothesis. 



c. 1004 : 351-353, La Place's Nebular Hypothesis. 



d. 1004 : 353-354. Lockyer's Meteoritic Hypothesis. 



e. 1301 : 27-31. The Nebular Hypothesis. 

 /. 1305:38. The Nebular Theory. 



g. 1306 : 19-22. The Nebular Hypothesis. 



