EECEKT FOEMATIONS. 



RECENT OR POST-TERTIARY FORMATIONS LATEST CHAPTER IN GEO- 

 LOGICAL HISTORY FLUVIATILE : DALES AND RIVER-TERRACES 

 LACUSTRINE : ALLUVIAL FLATS AND STRATHS ESTUARINE : PLAINS 

 AND DELTAS MARINE : SILTS, SAND-DRIFTS, AND RAISED BEACHES 

 CHEMICAL : MINERAL PRECIPITATES AND EXUDATIONS OR- 

 GANIC ! VEGETABLE AND ANIMAL GROWTHS VOLCANIC : LAVAS, 

 TUFAS, ETC. EXTENT AND VARIETY OF RECENT FORMATIONS 

 THEIR STUDY THE KEY TO THOSE OF EARLIER DATES CHRONOLO- 

 GICAL ARRANGEMENT OF HISTORIC AND PRE-HISTORIC HUMAN 

 AND PRE-HUMAN. 



As the glacial epoch, with its bouldery clays and gravels, 

 formed a limit to the tertiary system over a large portion 

 of the northern hemisphere at least so within the same 

 latitudes it constitutes an equally decided basement for 

 what are usually termed the Post-tertiary, or recent forma- 

 tions. Of course, like other appellations in geology having 

 reference to time, these terms are merely relative, embracing 

 accumulations that have taken place within the current 

 century, and others that may have been formed fifty or a 

 hundred thousand years ago, but still recent when compared 

 with those of the tertiary and other preceding systems. 

 This is all that is meant by the title at the head of the 

 present Sketch ; and whether we adopt Quaternary, Post- 

 tertiary, or Eecent designations all employed by geologists 

 in describing these formations it matters little so long as it 

 is understood that the events referred to have taken place 

 subsequent to the glacial era. These events, recent though 



