GENERAL REMARKS. 675 



creatures began to inhabit the earth after its crnst, which 

 was previously in a hquid state, had cooled down, and 

 the action of physical causes, such as water and air, 

 had commenced to form sedimentary rocks, in which 

 the bones and other remains of then-existing; animals 

 became entombed as fossils. Thus, through countless 

 ages, a history of animal life has been written in stone 

 by the hand of Time. The last leaves of this book lie 

 uppermost, while the first ones — unfortunately no longer 

 legible — repose on fused rock, of which granite is a 

 familiar example. This history is usually divided into 

 (i) Archaean, in which no trace of animal or vegetable 

 life is to be found ; (2) Primary ; (3) Secondary ; (4) 

 Tertiary ; and (5) Quaternary (Post-Tertiary). The Ter- 

 tiary period is divided into the Eocene (dawn of the 

 recent), Miocene (less recent), and Pliocene (more re- 

 cent) periods. The Quaternary includes the time from 

 the close of the Tertiary to the present day, and is 

 divided into the Pleistocene (Great Ice Age) and Re- 

 cent. The last-mentioned period is that during which 

 the existence of man became a prominent feature in 

 the history of the earth, and is divided into Prehistoric 

 and Historic. The Prehistoric cycle of time is divided 

 into : (i) Palaeolothic or Older Stone Age. (2) Neo- 

 lithic or Newer Stone Age, and (3) Bronze Age. The 

 Palaeolithic has been subdivided into the older or Mam- 

 moth Age, and the newer or Reindeer Age. In Palaeo- 

 lithic times, the most elaborate weapons and implements 

 made by man consisted merely of roughly chipped stones 

 (generally flint) or bones, and the use of metals was 

 entirely unknown. "The later or polished Stone Age; 

 a period characterised by beautiful weapons and instru- 

 ments made of flint and other kinds of stone, in which, 

 however, we find no trace of the knowledge of any metal 

 excepting gold, which seems to have been sometimes 

 used for ornaments. This we may call the Neolithic 

 period " {Avehury). By the advent of the Bronze Age, 



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