202 TERTIARY TIMES. 



these sediments, or rather formations of sediments, were 

 highly fossiliferous, they were covered over, at least in the 

 greater portion of the northern hemisphere, by thick masses 

 of bonldery clay and gravel, devoid, or all hut devoid, of 

 fossils; and this bouldery clay was considered as necessarily 

 limiting or closing the system. In this way the Tertiary 

 of the earlier geologists became to be broken up into Ter- 

 tiary and Quaternary the former embracing all the strata 

 that lie between the Chalk and Boulder-Clay, and the 

 latter the boulder-clay and all those superficial accumula- 

 tions that have since been formed, or are still in process of 

 formation, by the ordinary agencies of nature. Tabulating 

 this arrangement, we have the 



QUATERNARY, or POST - TERTIARY, embracing all the 

 superficial clays and gravels, the peat-mosses, swamp- 

 growths, coral-reefs, lake-silts, 'estuary-silts, and sea- 

 silts, with the boulder-clay beneath ; and the 



TERTIARY, all the regularly stratified clays and gravels, 

 marly limestones, gypsums, and lignites or brown- 

 coals, that lie between the Boulder-Clay and the Chalk 

 formations. 



In other words, the Quaternary or Post-Tertiary embraces 

 the rocks and records of the current epoch ; the Tertiary, 

 the rocks and records of a period that long preceded. And 

 this not a brief period, but one of long continuance so 

 long, that during its currency there were many oscillations 

 of sea and land, many extinctions of genera and species, 

 and many introductions of other and newer races. 



As might be expected in a system embracing a long 

 period of time, the rocks and fossils of the earlier tertiaries 

 differ considerably from those of the later ; and hence their 

 familiar arrangement into lower, middle, and upper; or 



