78 TERTIARY FORMATION. 



3. The Tertiary Formation is divided into the older, middle, and 

 newer tertiary groups, which have been conveniently designated 

 by Mr. Lyell under the names of Eocene, Miocene, and Pliocene. 



The first, EOCENE (from the Greek, eos, dawn, and kainos, 

 recent), designates the older tertiary strata, in which there appears, 

 as it were, the first dawn of existing species. 



The second, MIOCENE (from the Greek, meidn, less, and kainos, 

 recent), is applied to the middle tertiary strata, because in them we 

 find more recent species than in the preceding group, but still 

 fewer recent than extinct species. 



The third, PLIOCENE (from the Greek, pleidn, more, and kainos, 

 recent), is given to the newer tertiary beds, because there is always 

 a greater number of recent than of extinct species found in them. 



4. The Eocene, or older tertiaries. The beds thus designated 

 are a very variable series, consisting, in England and Belgium, of 

 stiff clays alternating with sand, and resting on coarse sand and 

 gravel ; and, in Paris, of a number of limestones and marls, alter- 

 nating with gypsum and silicious strata. They are deposited in 

 basin-shaped depressions in the older rocks, and in England some 

 portion of them has been so greatly disturbed, that the beds are 

 actually vertical. 



5. The older tertiaries of England are chiefly confined to three 

 masses, contained in trough-shaped basins, called respectively, the 

 London, the Hampshire, and Isle of Wight basins ; a stiff clay 

 predominates in them, and, from being very abundant near Lon- 

 don, is known as the " London day" The London clay often, 

 but not alw r ays, rests on a series of" sandy and gravelly beds, in- 

 closing bands of potters' clay, to which the name of Plastic day 

 has been given. 



6. The greatest development of eocene strata in the United 

 States occurs in Virginia, North and South Carolina, Georgia, and 

 Alabama. In Virginia these beds consist of greenish sands, nearly 

 identical in appearance with a portion of the creta'ceous series, and 

 of the same mineral composition ; and a little further to the south 

 a continuous formation of white limestone ("Santee limestone") 

 occurs, which is of no great thickness, and which varies in hard- 

 ness, and is composed of comminuted shells, but so closely resem 

 bling certain creta'ceous beds of the secondary period in New Jer- 

 sey, as to have been frequently mistaken for them. But this 

 resemblance does not extend to the fossil contents of the beds 



3. How is the tertiary period divided ? What is meant by Eocene ? 

 What by Miocene ? What by Pliocene ? 



4. What are the characters of the Eocene beds ? How are they de- 

 posited ? 



5. What are the chief localities of Eocene beds in England? What if 

 London clay ? 



C In what parts of the United States do Eocene strata exist? 



