THE BOWLDER CLAY. 349 



introduction of the post-glacial series — yet the oscilla- 

 tions of climate during the tertiary period begin as well 

 as end with these." — The Reader, London, 1865, p. 466. 



Having the grand outlines of this formation thus 

 mapped out for us, it remains for geologists in this coun- 

 try to see how far the parallel can be carried out in 

 America. There is as yet everything to be learned of 

 the lowest and oldest bowlder clay of the coast of Maine \ 

 to ascertain how far it is conformable with the brickyard 

 clays of the uplands, and whether there is an overlying 

 bed of sand such as the sheets of sand resting every- 

 where on the upper bowlder clay. At present there 

 have been revealed no signs of this lower bed of sand 

 clay, and the lowest clay beds we are acquainted with 

 seem to graduate into the rewashed, more inland, and 

 more recent bowlder or brickyard clays. 



In adopting the term Quaternary Period, we would 

 use it in the amended sense proposed by D'Archiac in 

 1848, in his " Histoire des Progrfes de la Geologic." 

 From his able review of all the prime characteristics so 

 trenchantly dividing this period from the Pliocene Ter- 

 tiary, we are led with that author to consider this period 

 as rather equivalent to the Tertiary as a whole, than to 

 either of its three subdivisions ; and rather as the begin- 

 ning of a new epoch or period, than the close of the 

 Tertiary. The distinctions, as shown by D'Archiac, ob- 

 tain no less in the tropics than in the high latitudes. In 

 tropical America the period is marked off from the Ter- 

 tiary by the appearance of the great mammals, the Her- 

 bivores characterizing the formation in America, and the 

 great Carnivores the deposit of the Eastern hemisphere. 

 About the Mediterranean the Tertiary Period closed 



