84 DOCTRINE OF EVOLUTION 



determine the approximate length of time required for 

 the construction of sedimentary rocks hke those which 

 natural agencies are producing to-day, there are few 

 definite facts to guide speculation as to the mode or 

 duration of the process by which the first hard crys- 

 talline surface of the earth was formed. But palaeon- 

 tology does not care so much about the earliest 

 geological happenings, for it is concerned with the 

 manifold animal forms that arose and evolved after life 

 appeared on the globe. Questions as to the way life 

 arose, and as to the earliest transformations of the 

 materials by which the earth was first formed are not 

 within the scope of organic evolution, although they 

 relate to intensely interesting problems for the student 

 of the process of cosmic evolution. 



According to the account now generally accepted, the 

 original material of the earth seems to have been a 

 semi-solid or semi-fluid mass formed by the condensation 

 of the still more fluid or even gaseous nebula out of 

 which all the planets of the solar system have been 

 formed and of which the sun is the still fiery core. As 

 soon as the earth had cooled sufficiently its substances 

 crystallized and wrinkled to form the first mountains 

 and ridges ; between and among these were the basins 

 which soon filled with the condensing waters to become 

 the earliest lakes and oceans. The wear and tear of 

 rains and snows and winds so worked upon the surfaces 

 of the higher regions that sediments of a finer or coarser 

 character like sand and mud and gravel were washed 

 down into the lower levels. These sediments were 

 afterwards converted into the first rocks of the so-called 

 stratified or sedimentary series, as contrasted with the 



