274 SCIENCE PROGRESS 



mediate forms have yet to be discovered, the probable conclusion 

 is that, in all districts of the world where seemingly from a 

 cursory reading of the signs sedimentation may have proceeded 

 continuously, there is a gap implying a large lapse of time. 

 The conclusion that emerges is that between the deposition of 

 the two sets of strata there have been considerable and world- 

 wide changes in the configuration of land and sea. And if that 

 be so, it does not seem absurd to suggest that there may, after 

 all, be a very close relation between the amount of change in 

 any dominant form and the time that has elapsed, respectively, 

 in the formation of sediments and in the unknown era repre- 

 sented by the intervening gaps. The elucidation of the precise 

 relation demands careful research of some particular period, 

 and that the numerous facts known concerning graptolites and 

 ammonites (to mention the groups principally used in zonal 

 classification) should be correlated in a more intelligent manner. 

 The few suggestions contained in this essay are tentative 

 and illustrative. They are but anticipations and indications of 

 the manner in which the twin subjects of organic evolution and 

 geologic time can be more intimately connected. To do more 

 would be difficult in the present state of scientific knowledge 

 and opinion. For fuller information the great necessity is 

 careful, detailed, and independent research. It is necessary that 

 the fundamental problem of geology should be deemed more 

 worthy of time and attention than the minor questions which 

 everywhere receive such detailed treatment and which result in 

 so many carefully written and voluminous monographs. The 

 subject is as yet hardly touched, and a clearer and more 

 wonderful science of geology can be built up by those who apply 

 to it true methods of scientific investigation. 



What we are entitled to say on the evidence before us, 

 biological, geological, and physical, is this : It would be absurd 

 to attempt, on very insufficient data, to give an estimate of the 

 probable lapse of geologic time. But there is, at the present 

 day, no reason whatever why it should not be a thousand million 

 of years or a time even greater. The hundred-million maximum of 

 the old physicist and geologist is now exploded. To make any 

 estimate in the place of that which has been shown to be invalid 

 will only be possible after long and careful research. It is hoped 

 that the criticisms and suggestions contained in this paper may do 

 something to show on what lines such research should proceed. 



