ELEMENTS OF THE GEOLOGICAL TIME- SCALE. 295 



may include the Oligocene to the top of the Hempstead beds. I 

 realize that such a proposition furnishes many points for dispute. 

 The scale is open for correction, and the standard may be 

 defined with greater precision. But it is offered as a working 

 hypothesis, to aid and stimulate investigation. 



Such a standard time -scale of geochronology, on the basis of 

 the Eocene period for a time -unit or geoehrone would read as 

 follows : 



Recent ) ^ 



Quaternary \ 



Pliocene ) |- = 3- 



Miocene 

 Eocene i J 



Cretaceous 

 Jurassic 

 Triassic 

 Carboniferous 6 



Devonian 5 



Up. Silurian 4 



Low. Silurian 

 or Ordovician 





45- 



15 



Cambrian 1 5 ) 



The proximity of the Eocene of the Gulf border to contin- 

 ental conditions now in operation, the abundance of its marine 

 fauna for comparison with like faunas of earlier or later age and 

 of the same or different habitats, and its inclusion of traces of 

 land-life for correlation with other conditions, and, in general, 

 the wide distribution of available Eocene deposits and faunas for 

 comparative study, are reasons for calling attention of investi- 

 gators to this particular field for minute investigation in perfect- 



ing the geological time -scale. 



Henry S. Williams. 



