LESSONS IN GEOLOGY. 



LESSONS IN GEOLOGY. XXV. 



THE TEUTIARY 8Y8TK.M. 



WE now enter, geologically speaking, modern times. The beds 

 of the Tertiary, and tlioir fossil contents, offer many a night ut 

 least not unfamiliar to modern observation. From the similarity 

 of the forms of life of the Tertiary epoch to those animals which 

 now people the earth, the period, looking at it from this point 

 of view, has been termed Cainozoic. The exact scale of the 

 inclination by which the past rises into the present has been 

 used by Lyell to separate the Tertiary into three divisions. M. 

 Deshayes examined some 3,000 Tertiary shells, comparing them 

 with existing species. In the lower Tertiary, which is found in 

 the neighbourhoods of London and Paris, 3*5 per cent, of the 



144 



The npper division is the Pliocene (Aiw, pli'-on, won ; and 

 teapot, recent), an it contains more recent specie* than any of 

 the lower beds. It is needless, perhaps, to observe that the 

 words in brackets following the Greek forms are merely 

 intended to give the reader who is unacquainted with Greek a 

 suitable idea of the way in which these words should be pro- 

 nounced. As in other parts of tbo POPULAR EDUCATOR, the 

 sounds of the Greek words are represented phonetically. 



The Tertiary, as a whole, U not so clearly defined as the 

 deposits of the preceding periods. However, the following 

 synopsis will give the student some indication of the localities 

 and the appearances of the beds. The limits of our space compel 

 us to treat of the English Tertiaries mainly, although the 

 deposits do not find in our island a typical development. 



137 



fossila proved to be of species still in existence. From the 

 middle Tertiary of the Loire and Gironde 17 per cent, were 

 found to have representatives now alive ; while the upper Ter- 

 tiary or sub-Apennine beds yielded from 37 to 50 per cent, of 

 existing species. Further south, in Sicily, are much newer 

 Tertiary beds, rising above the sea to a great thickness, and the 

 fossils in these exhibited, with a very few exceptions only 5 

 per cent. the same life as is to-day existing in the Mediter- 

 ranean Sea. This brought the deposition of these beds into 

 recent times, and consequently geologists have separated them 

 away from the Tertiary, and classed them with recent deposits, 

 under the name of post-Tertiary. 



The lower, middle, and upper Tertiaries, mentioned above, are 

 now known by names bestowed upon them by Lyell. The 

 lowest is termed Eocene, from jja-s (e'-ose, the davm) and KCUVOS 

 (ki'-nos, recent) the dawn of new or recent times. The central 

 division is the Miocene (utiov, mi'-on, less, and Koiror, recent) a 

 term intended to express a tnincw proportion of recent species. 

 141 N.B. 



PLIOCEKI. 



MlOCEHI." 



EOCENE. 



Norwich crag, which entombs the bones of extinct 



mammals, and consists of beds of sand, clay, and 



gravel. 

 Rtd cray of Suffolk is a loamy sand, tinted with iron 



oxide. 

 Coralline crag of Suffolk, a concrete of shells and corals, 



now loose in calcareous sand, now consolidated into 



limestone beds, sometimes sufficiently compact for 



building-stone. 

 Hempstead bed*. Isle of Wipht, are of this period, and 



reach some 170 feet in thickness. 

 The LigniUt of Bovey Trcuxy. 

 The Leaf bed* of Mull. 

 Liynite* of Antrim. 



FIuvio-mann beds of Hampshire and the Isle of Wight. 

 Bagshot sands. 

 London clay. 

 Bognor beds. 

 H'oohrt'cfi clay*. 

 Thanet lands. 



