THE CHANGING WORLD 



XXI 



TIME SPENT (PALEONTOLOGY) 



Preview. The stretch of time • Measures of time • Kinds of fossils • 

 Fossils as time markers • The testimony of extinct types • The role of pale- 

 ontology • Suggested readings. 



PREVIEW 



There are two things with which living creatures are inseparably 

 involved and from which there is no escape, space and time. 



Although everyone has a working idea of what is meant by these two 

 common words and uses them freely and constantly in all sorts of con- 

 nections, it is somewhat surprising how difficult it is to define them 

 satisfactorily without making use of other words that require definition 

 as well. Try it ! Just what is time ? Do not resort to the dictionary 

 until you are willing to give up. You will probably find the dictionary 

 disappointing. Is time, perhaps, that particular bit of eternity to 

 which we can set limits? If so, what is eternity? 



There are two sciences in this connection that are profitable to 

 explore, if only to enlarge our intellectual sky lines. The first and 

 older science is Astronomy, which serves to expand our ideas of space, 

 and of which man alone can have any inkling. The second is Paleon- 

 tology. Although this has been developed more recently, it is never- 

 theless concerned with very old things. One benefit to be gained from 

 the study of paleontology is that it stretches, and makes more spa- 

 cious, our concept of time. 



It is not the purpose of this section to present an outline of paleon- 

 tology, but simply to consider very briefly the relation between time 

 and living things. The role of living things with reference to space 

 has already been touched upon in unit II under the title, "The 

 Biological Conquest of the World." 



The Stretch of Time 



Whatever time is, the geologist has plenty of convincing evidence 

 that an enormous amount of it already has been spent upon this earth 

 since it became the earth, for time was passing, ''with no vestige of a 



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