Chapter Two 

 THIRTY MILLION GENERATIONS 



WHEN it was said that Coelacanths had been thought to be 

 extinct for 50 miUion years, many people found it fantastic 

 that scientists should even be prepared to make statements of 

 that type. Such a period of time is of course enormous, but it is 

 short compared with the time that covers the full history of our 

 earth. Before we can show where the Coelacanth fits, it would be 

 advantageous to make a rapid survey of what scientists now be- 

 lieve lies behind us. 



Although fossils have been known for quite a long time, it is 

 astonishing that their true significance has been realised only in 

 comparatively recent times. One of the earliest fossils to be de- 

 scribed was an almost perfect skeleton of a large salamander, 

 found in rock strata in Germany, and it was regarded as the 

 remains of *a poor sinner overwhelmed by the [Biblical] 

 flood'. 



The science of Talaeontology' (knowledge of old life) is in one 

 sense quite new, and in the last half-century it has developed in a 

 manner that the first workers could scarcely have foreseen. In 

 less than a century of intensive work some of the most remarkable 

 intellects of all time have, from often only ffagmentary remains, 

 been able to unravel much of the history of life from the most 

 remote past until today, and to present an almost complete picture 

 of the main forms of life that have inhabited the earth. With this 

 has come a rapidly increasing perception of the vast ages that lie 

 behind us, and methods have been developed by which it has 

 become possible to construct a scale to measure past time in a 

 manner undreamt of not so long ago. The methods by which this 

 is done are highly technical, and still newer and finer techniques 

 are continually being developed. 



Many people are curious about this. Here is one method by 

 which the approximate age of a rock may be found. Uranium 



