THE CENTURY'S PROGRESS IN GEOLOGY 



It must not be sup- 

 posed, however, that 

 the successive "ages" 

 of the geologist are 

 shut off from one an- 

 other in any such ar- 

 bitrary way as this ver- 

 bal classification might 

 seem to suggest. In 

 point of fact, these 

 "ages" have no better 

 warrant for existence 

 than have the "cen- 

 turies" and the "weeks" 



of e Very-day COmptlta- GEORGE POULETTE SCROPE, F.R.a 



tion. They are convenient, and they may even stand 

 for local divisions in the strata, but they are bounded by 

 no actual gaps in the sweep of terrestrial events. 



Moreover, it must be 

 understood that the 



"ages" of different 

 continents, though de- 

 scribed under the same 

 name, are not neces- 

 sarily of exact contem- 

 poraneit} 7 . There is no 

 sure test available by 

 which it could be 

 shown that the Devo- 

 nian age, for instance, 

 as outlined in the 

 strata of Europe, did 

 not begin millions of 



SIR CHARLES LYELL, BART, F.R.S. 



141 



