THE EARLIEST MEN 165 



We have now to turn to the subject of Geological 

 Time, with which a portion of our subject is in- 

 separably bound up. Indeed, as some writer has 

 very aptly remarked, the problem of early man is 

 far more a problem of geology than a problem of 

 biology. 



Here again it has to be remarked that the use 

 of the word " time " in connection with geology, 

 is more than a little misleading. As in the case of 

 archaeology, " time " in the sense of a definite 

 number of years can, as we shall shortly see, be 

 applied only in the most tentative manner to 

 geological epochs. We can, with more or less cer- 

 tainty, divide up the history of the world into 

 geological eras, and, though not always with com- 

 plete certainty, assign a given rock bed to its 

 appropriate era, but when we come to attempt 

 any method of dating, in terms of years, the time 

 when this era was in being, we find ourselves con- 

 fronted with a hitherto insuperable problem. 



Stratigraphically, however, we may divide 

 Geological " Time " into Primary or Palaeozoic 

 Secondary or Mesozoic ; Tertiary or Cainozoic, 

 and Quaternary or Post-Tertiary. With the first 

 two of these, comprising vast areas of rock, and 

 formed during vast, almost inconceivable ages of 

 the world's history, we have nothing to do in 

 these notes, since man is not directly connected 

 with them. But in order to follow what has yet 

 to come, it is necessary to deal somewhat more 

 particularly with the two latest of these periods, 

 and proceeding from the earlier to the later, we 

 may set down the following classification : 



