THE WORLD BEFORE LIFE. 527 



determinate form. Next comes the history of the processes by which 

 system is induced. There were hollows and valleys in those early 

 times, most probably vast and deep, but not irregular. The constant 

 fall of rain must originate brooks and streams, coursing their down- 

 ward way toward the lowest levels. Animated with this descending 

 impulse, they remove barriers at the outlets of lakes and pools, exca- 

 vate gorges through ridges of impediment, and wear off numerous frag- 

 ments from every projecting point. This eroded material would be 

 urged forward by the current till the lowest possible level was reached, 

 probably the bottom of an arm of the sea or bay, and remain there 

 while the basin was filling up. Thus we should have a formation, 

 composed of layers of the sand, clay, and limestone, originally a chem- 

 ical precipitate, but now altered into sedimentary deposits. When 

 the first accessible hollows had been filled up, a great interval of 

 time had elapsed, and the external envelope of the earth would 

 shrink, on account of its refrigeration, and fall upon the collapsed nu- 

 cleus. Hence new valleys would be formed, and the streams would 

 carry the detritus into them, and another set of strata lying upon the 

 edges of the first formation would be deposited. This process has 

 been going on uninterruptedly from that day to the present, and the 

 face of the earth has been changed a hundred times. How long this 

 process went on before the introduction of life it is impossible to say, 

 for the oldest strata known to exist contain the remains of the Eozoic 

 reef-building colonies, in the formations known as the Laurentian. 



As some of the older Laurentian beds are composed of pebbles, it 

 is obvious that earlier formations exist, from which the sedimentary 

 material has been derived. Possibly we may be able ultimately to 

 separate from the various systems of the age under consideration those 

 characterized by the presence of the first existing plants — since in the 

 order of Nature there must have been plants before animals. If we 

 follow the analogy of the duration of the earlier periods, we may be- 

 lieve that this JEophytic age exceeded the Eozoic in length ; and, fur- 

 thermore, that the time before the introduction of life was far greater 

 than what has lapsed subsequently. If the law admits of universal 

 application, that the simpler the organism the longer it has lived, then 

 we may perhaps claim that the earlier the period the greater has been 

 its duration. The extent of work performed in these early ages has 

 certainly far exceeded any thing yet known of the operations in the 

 Zoic periods. 



The series of changes prior to the introduction of life may therefore 

 be registered as distinct ages, as well marked by special features and 

 a natural order of succession as the periods defined by Paleontology. 

 The minute details of the history are wanting, but, with such sub- 

 stantial bases of probability as have been set forth, human thought 

 will construct theoretical systems that will command universal ac- 

 ceptance. 



